Inverse Association of Plasma Molybdenum with Metabolic Syndrome in a Chinese Adult Population: A Case-Control Study

Molybdenum has been found to be associated with metabolic disorders. However, the relationship between molybdenum and metabolic syndrome (MetS) is still unclear. A large case-control study was conducted in a Chinese population from the baseline of Ezhou-Shenzhen cohort. A total of 5356 subjects were included with 2678 MetS and 2678 controls matched by sex and age (±2 years). Medians (IQRs) of plasma molybdenum concentrations were 1.24 μg/L for MetS cases and 1.46 μg/L for controls. After adjustment for multiple covariates, the odds ratio (OR) and 95% confidence intervals (CIs) for MetS were 1.00 (reference), 0.71 (0.59-0.84), 0.56 (0.46-0.68), and 0.47 (0.39-0.58) across quartiles of plasma molybdenum, and per SD increment of log-transformed molybdenum was associated with a 23% lower risk of MetS. In the spline analysis, the risk of MetS and its components decreased steeply with increasing molybdenum and followed by a plateau when the cutoff point was observed around 2.0 μg/L. The dose-dependent relationship of molybdenum with MetS remained consistent when considering other essential elements in the Bayesian kernel machine regression (BKMR) model. In our study, higher plasma molybdenum was significantly associated with a lower risk of MetS, as well as its components, in a dose-response manner.

[Metabolic correction: a biochemical option against diseases]

Human development and its physiology depends on a number of complex biochemical body processes, many of which are interactive and codependent. The speed and the degree in which many physiological reactions are completed depend on enzyme activity, which in turn depends on the bioavailability of co-factors and micronutrients such as vitamins and minerals. To achieve a healthy physiological state, organism need that biochemical reactions occur in a controlled and specific way at a particular speed and level or grade fully completed. To achieve this, is required an optimal metabolic balance. Factors such as, a particular genetic composition, inadequate dietary consumption patterns, traumas, diseases, toxins and environmental stress all of these factors rising demands for nutrients in order to obtain optimal metabolic balance. Metabolic correction is a biochemical and physiological concept that explains how improvements in cellular biochemistry of an organism can help the body achieve metabolic and physiological optimization. We summarize the contribution of several pioneers in understanding the role of micronutrients in health management. The concept of metabolic correction is becoming a significant term due to the presence of genetic variants that affect the speed of reactions of enzymes, causing metabolic alterations that enhance or promote the state/development of multiple diseases. Decline in the nutritional value of the food we eat, the increase in demand for certain nutrients caused by normal development, diseases and medications induce, usually, nutrients consumption. These nutritional deficiencies and insufficiencies are causing massive economic costs due to increased morbidity and mortality in our society. In summary, metabolic correction improves the enzymatic function, which favors the physiological normal functions, thus, contributing to improving health and the welfare of the human being. The purpose of this paper is to describe and introduce the concept of optimal metabolic correction as a functional cost-effective mechanism against disease, in addition, to contribute to diseases prevention and regeneration of the body and health.

Lipophilic modification enhances anti-colitic properties of rosmarinic acid by potentiating its HIF-prolyl hydroxylases inhibitory activity

Inhibition of hypoxia inducible factor-prolyl hydroxylase-2 (HPH), leading to activation of hypoxia inducible factor (HIF)-1 is a potential therapeutic strategy for the treatment of colitis. Rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid is a naturally occurring polyphenolic compound with two catechols, a or inhibition of HPH. To improve accessibility of highly hydrophilic RA to HPH, an intracellular target, RA was chemically modified to decrease hydrophilicity. Of the less-hydrophilic derivatives, rosmarinic acid methyl ester (RAME) most potently inhibited HPH. Accordingly, RAME prevented hydroxylation of HIF-1α and consequently stabilized HIF-1α protein in cells. RAME inhibition of HPH and induction of HIF-1α were diminished by elevated doses of the required factors of HPH, 2-ketoglutarate and ascorbate. RAME induction of HIF-1α led to activation of an ulcer healing pathway, HIF-1-vascular endothelial growth factor (VEGF), in human colon carcinoma cells. RAME administered rectally ameliorated TNBS-induced rat colitis and substantially decreased the levels of pro-inflammatory mediators in the inflamed colonic tissue. In parallel with the cellular effects of RAME, RAME up-regulated HIF-1α and VEGF in the inflamed colonic tissue. Thus, lipophilic modification of RA improves its ability to inhibit HPH, leading to activation of the HIF-1-VEGF pathway. RAME, a lipophilic RA derivative, may exert anti-colitic effects via activation of the ulcer healing pathway.

The biochemical roots of the RNA world: from zymonucleic acid to ribozymes

The history of the ideas that led to the RNA World hypothesis is reviewed. As the understanding of the properties of RNA molecules progressed, the evolutionary interpretation of their genetic properties and widespread distribution in intracellular environments, as well as the catalytic properties of nucleotide coenzymes and the participation of RNA monomers in metabolic pathways, led to several independent proposals of protein-free primordial life forms. Current ideas on the RNA World are part of a long and storied scientific perspective in which these different hypotheses were developed. However, the lack of continuity between them may be explained in part by the absence of an evolutionary framework that characterized the early development of molecular biology, as well as by the demise of certain areas of research like coenzyme chemistry.

Vitamin B6: beyond coenzyme functions

Endogenous reactive intermediates such as photoexcited states of tissue chromophores, reactive oxygen species (ROS), reactive carbonyl species (RCS), and transition metal ions are mediators of tissue damage involved in initiation and progression of human pathologies including tumorigenesis, atherosclerosis, diabetes, and neurodegenerative disease. A large body of evidence now suggests that B6 vitamers antagonize the harmful activity of endogenous reactive intermediates fulfilling a very different role than that established as a cofactor for numerous enzymes. In this chapter, the structural basis of vitamin B6 activity as a potent antioxidant, metal chelator, carbonyl scavenger, and photosensitizer is presented and the physiological relevance is discussed.

Role of the azadithiolate cofactor in models for [FeFe]-hydrogenase: novel structures and catalytic implications

This paper summarizes studies on the redox behavior of synthetic models for the [FeFe]-hydrogenases, consisting of diiron dithiolato carbonyl complexes bearing the amine cofactor and its N-benzyl derivative. Of specific interest are the causes of the low reactivity of oxidized models toward H(2), which contrasts with the high activity of these enzymes for H(2) oxidation. The redox and acid-base properties of the model complexes [Fe(2)[(SCH(2))(2)NR](CO)(3)(dppv)(PMe(3))](+) ([2](+) for R = H and [2'](+) for R = CH(2)C(6)H(5), dppv = cis-1,2-bis(diphenylphosphino)ethylene)) indicate that addition of H(2) followed by deprotonation are (i) endothermic for the mixed valence (Fe(II)Fe(I)) state and (ii) exothermic for the diferrous (Fe(II)Fe(II)) state. The diferrous state is shown to be unstable with respect to coordination of the amine to Fe, a derivative of which was characterized crystallographically. The redox and acid-base properties for the mixed valence models differ strongly for those containing the amine cofactor versus those derived from propanedithiolate. Protonation of [2'](+) induces disproportionation to a 1:1 mixture of the ammonium [H2'](+) (Fe(I)Fe(I)) and the dication [2'](2+) (Fe(II)Fe(II)). This effect is consistent with substantial enhancement of the basicity of the amine in the Fe(I)Fe(I) state vs the Fe(II)Fe(I) state. The Fe(I)Fe(I) ammonium compounds are rapid and efficient H-atom donors toward the nitroxyl compound TEMPO. The atom transfer is proposed to proceed via the hydride. Collectively, the results suggest that proton-coupled electron-transfer pathways should be considered for H(2) activation by the [FeFe]-hydrogenases.

Functional connections and pathways of coenzyme Q10-inducible genes: an in-silico study

Coenzyme Q10 (CoQ10, ubiquinone) is an essential cofactor in the electron transport chain, serves as a potent antioxidant in mitochondria and lipid membranes, and is often used as a dietary supplement for a number of diseases including cardiovascular diseases. Recently, we obtained evidence that CoQ10 (Kaneka Q10) affects the expression of hundreds of human genes. To decipher the functional and regulatory connections of these genes, a literature search combined with transcription factor binding site analysis was performed using Genomatix BiblioSphere and MatInspector. This in-silico analysis revealed 17 CoQ10-inducible genes which are functionally connected by signalling pathways of G-protein coupled receptors, JAK/STAT, integrin, and beta-arrestin. Promoter analysis of these CoQ10-inducible genes showed one group of NF B-regulated genes, namely IL5, thrombin, vitronectin receptor and C-reactive protein (CRP). Furthermore, a common promoter framework containing binding sites of the transcription factor families EVI1, HOXF, HOXC, and CLOX was identified in the promoters of IL5, CRP, and vitronectin receptor. The identified CoQ10-inducible genes and pathways play an important role in inflammatory response. Since these effects are based on an in-vitro study, the effect of CoQ10 on vascular health in vivo needs to be addressed in further animal and/or human intervention studies.

Roles of vitamins B5, B8, B9, B12 and molybdenum cofactor at cellular and organismal levels

Many efforts have been made in recent decades to understand how coenzymes, including vitamins, are synthesised in organisms. In the present review, we describe the most recent findings about the biological roles of five coenzymes: folate (vitamin B9), pantothenate (vitamin B5), cobalamin (vitamin B12), biotin (vitamin B8) and molybdenum cofactor (Moco). In the first part, we will emphasise their biological functions, including the specific roles found in some organisms. In the second part we will present some nutritional aspects and potential strategies to enhance the cofactor contents in organisms of interest.

Coenzyme Q10 supplementation and heart failure

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the Western world. Oxidative stress appears to play a pivotal role in atherosclerosis. Coenzyme Q10 (CoQ10), one of the most important antioxidants, is synthesized de novo by every cell in the body. Its biosynthesis decreases with age and its deficit in tissues is associated with degenerative changes of aging, thus implicating a possible therapeutic role of CoQl0 in human diseases. There is evidence to support the therapeutic value of CoQ10 as an adjunct to standard medical therapy in congestive heart failure. However, much further research is required, especially in the use of state-of-the-art techniques to assess functional outcomes in patients with congestive heart failure.

On reaction dynamics at dopamine synapses

Dopamine neurons play a key role in normal and pathological cognitive processes as well as in the effects of certain drugs of addiction. Models of the synapses of such neurons include transporter mechanisms and reaction dynamics. This article focuses attention on the fundamental reaction that converts tyrosine to DOPA, which involves a cofactor. The Michaelis-Menten formula for the rate of an enzymatic reaction is modified by the presence of cofactors, which may be either essential or nonessential. In the essential case, the reaction rate is found to depend on the relative magnitudes of the concentrations of the primary enzyme and the cofactor. The case of a nonessential cofactor is more complex and it is shown for the first time how this leads to reaction rate formulas that depend explicitly on the concentrations of the enzyme and cofactor. The extended Michaelis-Menten formulas are applied to the aforementioned reaction with tyrosine hydroxylase as enzyme and biopterin as cofactor. The results are useful in constructing accurate models of dopamine synapses.

Coenzyme Q(10)--its role as a prooxidant in the formation of superoxide anion/hydrogen peroxide and the regulation of the metabolome

Coenzyme Q10 plays a central role in cellular bioenergy generation and its regulation. Closed membrane systems generate a proton motive force to create transient localized bio-capacitors; the captured energy is used for the synthesis of mitochondrial ATP but also for many other processes, such as metabolite translocations, nerve conduction and a host of other bioenergy requiring processes. Coenzyme Q10 plays a key role in many of these sub-cellular membrane energy generating systems. Integral to this phenomenon is the prooxidant role of coenzyme Q10 in generating the major superoxide anion/hydrogen peroxide second messenger system. This messenger system, largely but not exclusively, arises from coenzyme Q10 semiquinone function; it contributes to the regulation of sub-cellular redox potential levels; transcription/gene expression control; is essential for modulated protein turnover and activation; mediates hormone and growth factor extracellular signaling. The regulated prooxidant formation of the superoxide anion/H2O2 second messenger system is essential for the normal physiological function of the metabolome. The normally functioning metabolome is the expression of a finely tuned dynamic equilibrium comprised of thousands of anabolic and catabolic reactions and all cellular signaling systems must be finely regulated. There is still much to be learnt about the up/down regulation of the H2O2 messenger system. The concept that superoxide anion/H2O2 cause random macromolecular damage is rebutted. The administration of antioxidants to quench the inferred toxicity of these compounds as a therapy for age associated diseases is unsupported by extant mammalian clinical trials and should be subject to serious re-evaluation. The role of ascorbic acid as a beneficial hydrogen peroxide prodrug is discussed.

Coenzyme Q10 and statins: biochemical and clinical implications

Statins are drugs of known and undisputed efficacy in the treatment of hypercholesterolemia, usually well tolerated by most patients. In some cases treatment with statins produces skeletal muscle complaints, and/or mild serum CK elevation; the incidence of rhabdomyolysis is very low. As a result of the common biosynthetic pathway Coenzyme Q (ubiquinone) and dolichol levels are also affected, to a certain degree, by the treatment with these HMG-CoA reductase inhibitors. Plasma levels of CoQ10 are lowered in the course of statin treatment. This could be related to the fact that statins lower plasma LDL levels, and CoQ10 is mainly transported by LDL, but a decrease is also found in platelets and in lymphocytes of statin treated patients, therefore it could truly depend on inhibition of CoQ10 synthesis. There are also some indications that statin treatment affects muscle ubiquinone levels, although it is not yet clear to which extent this depends on some effect on mitochondrial biogenesis. Some papers indicate that CoQ10 depletion during statin therapy might be associated with subclinical cardiomyopathy and this situation is reversed upon CoQ10 treatment. We can reasonably hypothesize that in some conditions where other CoQ10 depleting situations exist treatment with statins may seriously impair plasma and possible tissue levels of coenzyme Q10. While waiting for a large scale clinical trial where patients treated with statins are also monitored for their CoQ10 status, with a group also being given CoQ10, physicians should be aware of this drug-nutrient interaction and be vigilant to the possibility that statin drugs may, in some cases, impair skeletal muscle and myocardial bioenergetics.

Functional characterization of the major and minor phosphorylation sites of the P protein of Borna disease virus

The phosphoprotein P of Borna disease virus (BDV) is an essential cofactor of the viral RNA-dependent RNA polymerase. It is preferentially phosphorylated at serine residues 26 and 28 by protein kinase C epsilon (PKCepsilon) and, to a lesser extent, at serine residues 70 and 86 by casein kinase II (CKII). To determine whether P phosphorylation is required for viral polymerase activity, we generated P mutants lacking either the PKCepsilon or the CKII phosphate acceptor sites by replacing the corresponding serine residues with alanine (A). Alternatively, these sites were replaced by aspartic acid (D) to mimic phosphorylation. Functional characterization of the various mutants in the BDV minireplicon assay revealed that D substitutions at the CKII sites inhibited the polymerase-supporting activity of P, while A substitutions maintained wild-type activity. Likewise, D substitutions at the PKC sites did not impair the cofactor function of BDV-P, whereas A substitutions at these sites led to increased activity. Interestingly, recombinant viruses could be rescued only when P mutants with modified PKCepsilon sites were used but not when both CKII sites were altered. PKCepsilon mutant viruses showed a reduced capacity to spread in cell culture, while viral RNA and protein expression levels in persistently infected cells were almost normal. Further mutational analyses revealed that substitutions at individual CKII sites were, with the exception of a substitution of A for S86, detrimental for viral rescue. These data demonstrate that, in contrast to other viral P proteins, the cofactor activity of BDV-P is negatively regulated by phosphorylation.

Coenzyme Q10 in phenylketonuria and mevalonic aciduria

Mevalonic aciduria (MVA) and phenylketonuria (PKU) are inborn errors of metabolism caused by deficiencies in the enzymes mevalonate kinase and phenylalanine 4-hydroxylase, respectively. Despite numerous studies the factors responsible for the pathogenicity of these disorders remain to be fully characterised. In common with MVA, a deficit in coenzyme Q10 (CoQ10) concentration has been implicated in the pathophysiology of PKU. In MVA the decrease in CoQ10 concentration may be attributed to a deficiency in mevalonate kinase, an enzyme common to both CoQ10 and cholesterol synthesis. However, although dietary sources of cholesterol cannot be excluded, the low/normal cholesterol levels in MVA patients suggests that some other factor may also be contributing to the decrease in CoQ10.The main factor associated with the low CoQ10 level of PKU patients is purported to be the elevated phenylalanine level. Phenylalanine has been shown to inhibit the activities of both 3-hydroxy-3-methylglutaryl-CoA reductase and mevalonate-5-pyrophosphate decarboxylase, enzymes common to both cholesterol and CoQ10 biosynthesis. Although evidence of a lowered plasma/serum CoQ10 level has been reported in MVA and PKU, few studies have assessed the intracellular CoQ10 concentration of patients. Plasma/serum CoQ10 is influenced by dietary intake as well as its lipoprotein content and therefore may be limited as a means of assessing intracellular CoQ10 concentration. Whether the pathogenesis of MVA and PKU are related to a loss of CoQ10 has yet to be established and further studies are required to assess the intracellular CoQ10 concentration of patients before this relationship can be confirmed or refuted.

Coenzyme Q10 in cardiovascular disease

In this review we summarise the current state of knowledge of the therapeutic efficacy and mechanisms of action of CoQ(10) in cardiovascular disease. Our conclusions are: 1. There is promising evidence of a beneficial effect of CoQ(10) when given alone or in addition to standard therapies in hypertension and in heart failure, but less extensive evidence in ischemic heart disease. 2. Large scale multi-centre prospective randomised trials are indicated in all these areas but there are difficulties in funding such trials. 3. Presently, due to the notable absence of clinically significant side effects and likely therapeutic benefit, CoQ(10) can be considered a safe adjunct to standard therapies in cardiovascular disease.

Molecular mechanisms of HIV integration and therapeutic intervention

Retroviruses, such as human immunodeficiency virus type 1 (HIV-1), are plus-sense RNA viruses that require reverse transcription and then DNA integration to establish a chromosomal provirus as an obligate replication intermediate. The viral enzyme reverse transcriptase synthesises linear double-stranded cDNA, which is the template for the viral enzyme integrase. Integrase catalyses two separate chemical reactions: an initial 3' processing of the nascent cDNA ends, which is followed in the cell nucleus by their covalent attachment to the 5' phosphates of a double-stranded staggered cut in chromosomal DNA. As integrase activity is essential for productive retroviral infection, there is intense interest in developing small-molecule inhibitors of the HIV-1 enzyme to increase the breadth of the antiviral arsenal used to fight HIV/AIDS. Purified integrase protein displays the 3' processing and DNA-strand-transfer activities essential for cDNA integration in integration assays in vitro, but numerous studies indicate that cellular proteins play important roles during integration in infected cells. This review highlights the molecular mechanisms behind HIV-1 integration, focusing on recent insights into functions of human cellular cofactors. The progress towards developing integrase inhibitors for their use in the clinic is also reviewed.

Enhanced spatial ability in aged dogs following dietary and behavioural enrichment

We examined the benefits of a broad spectrum antioxidant diet and enrichment comprised of physical exercise, environmental stimulants and cognitive testing, on spatial memory performance in beagle dogs. Both aged (N=48) and young (N=16) beagle dogs (Canus familiaris) were tested yearly on a three-component delayed non-match to position spatial task for three consecutive years. The results showed that young enriched animals acquired the task in fewer sessions, made fewer errors, responded slower and made fewer positional responses, compared to aged enriched animals. An analysis restricted to aged animals revealed that antioxidant administration and enrichment resulted in fewer errors, slower responses and decreased positional responses, particularly in Year 3. Finally, cohort differences emerged, which exemplify the significance of early environmental intervention. Aged dogs that were housed with other animals and exposed to an outdoor environment in early development displayed greater benefits from both interventions. These findings indicate that long-term dietary intervention and enrichment can buffer age-associated cognitive decline.

Coactivation of estrogen receptor alpha (ER alpha)/Sp1 by vitamin D receptor interacting protein 150 (DRIP150)

Vitamin D receptor interacting protein (DRIP150) coactivates estrogen receptor alpha (ERalpha)-mediated transactivation in breast cancer cell lines transfected with a construct (pERE(3)) containing three estrogen responsive elements (EREs). In this study, we show that DRIP150 also coactivates ERalpha/Sp1-mediated transactivation in ZR-75, MCF-7, and MDA-MB-231 breast cancer cells transfected with a construct (pSp1(3)) containing three consensus GC-rich motifs. Studies on coactivation of wild-type and variant ERalpha/Sp1 by DRIP150 indicates that the DNA-binding domain and helix 12 in the ligand binding domain of ERalpha are required and the coactivation response is squelched by overexpressing an NR-box peptide that contains two LXXLL motifs from GRIP2. In contrast, coactivation of ERalpha/Sp1 by wild-type and mutant DRIP150 expression plasmids show that coactivation of ERalpha/Sp1 by DRIP150 is independent of the NR-boxes. Deletion analysis of DRIP150 demonstrates that coactivation requires an alpha-helical NIFSEVRVYN (amino acids 795-804) motif within 23 amino acid sequence (789-811) in the central region of DRIP150 and similar results were obtained for coactivation of ERalpha by DRIP150. Thus, although different domains of ERalpha are required for hormone-dependent activation of ERalpha and ERalpha/Sp1, coactivation of these transcription factors by DRIP150 requires the alpha-helical amino acids 795-804. This is the first report of a coactivator that enhances ERalpha/Sp1-mediated transactivation in breast cancer cells.

Metal and cofactor insertion

Cells require metal ions as cofactors for the assembly of metalloproteins. Principally one has to distinguish between metal ions that are directly incorporated into their cognate sites on proteins and those metal ions that have to become part of prosthetic groups, cofactors or complexes prior to insertion of theses moieties into target proteins. Molybdenum is only active as part of the molybdenum cofactor, iron can be part of diverse Fe-S clusters or of the heme group, while copper ions are directly delivered to their targets. We will focus in greater detail on molybdenum metabolism because molybdenum metabolism is a good example for demonstrating the role and the network of metals in metabolism: each of the three steps in the pathway of molybdenum cofactor formation depends on a different metal (iron, copper, molybdenum) and also the enzymes finally harbouring the molybdenum cofactor need additional metal-containing groups to function (iron sulfur-clusters, heme-iron).

Role of plasma as activator and cofactor in phosphorylation catalyzed by protein kinase C

The purpose of this study was to investigate whether plasma can influence the phosphorylation of protein kinase C (PKC). Lysate samples were prepared from normal skin or melanoma tissue and were reacted with a PKC peptide substrate in the presence or absence of plasma. In normal skin tissue lysates, the phosphorylation rates were much lower than those in melanoma tissue lysates. However, the level of phosphorylated peptide was increased in both normal skin and melanoma tissue lysates if plasma was present. Phosphorylation rates in the samples taken from the centre of B16 melanoma tissue were lower than those in samples taken from the edge. Moreover, addition of activator and/or cofactors (diacylglycerol, phosphatidylserine and/or Ca2+) of PKC, or plasma to the lysates contaminated by plasma had no effect on phosphorylation rates for the peptide substrate. These results indicate that plasma can play a role of activator and cofactor for substrate phosphorylation.

The essential requirement for superoxide radical and nitric oxide formation for normal physiological function and healthy aging

Contrary to the dogma that superoxide anion and hydrogen peroxide formation are highly deleterious to cell function and healthy aging, we suggest this premise is flawed. Superoxide anion and hydrogen peroxide formation are essential to normal cellular function; they constitute a second messenger system absolutely required for the regulation of the metabolome. Embraced within this regulation is the modulation of cellular redox poise, bioenergy output, gene expression and cell differentiation. A key component in the overall process is coenzyme Q10 whose prooxidant function through the formation of superoxide anion and hydrogen peroxide is a major factor in the overall processes. The free radical gas, nitric oxide (similarly to superoxide anion), functions in the regulation of a wide range of cell systems. As part of the normal physiological process, superoxide anion and NO function separately and interactively as second messengers. Superoxide anion and nitric oxide play an intrinsic role in the regulated ordered turnover of proteins, rather than randomly cause protein damage and their inactivation. The proposition that metabolic free radical formation is unequivocally deleterious to cell function is rebutted; their toxicity as primary effectors in the aging process has been overemphasized. The concept that a dietary supplement of high concentrations of small-molecule antioxidants is a prophylactic/amelioration therapy for the aging process and age-associated diseases is questioned as to its clinical validity.

[Biological function of CoQ10 and its effect on the quality of spermatozoa]

Oxidative damage is one of the important factors inducing the regression of sperm quality. CoQ10 is a liposoluble antioxidant that exists in mitochondria and its levels in semen and spermatozoa have an important role in the oxidation resistance of the male genital system. Exogenous administration of CoQ10 can improve the sperm quality and reproductive ability of infertile patients as well as exert the effects of an adjunctive therapy on male infertility. This review describes the biological function of CoQ10 and its effect on the quality of spermatozoa and its effect as an adjunctive therapy on male infertility.

Lysyl oxidase: an oxidative enzyme and effector of cell function

Lysyl oxidase (LOX) oxidizes the side chain of peptidyl lysine converting specific lysine residues to residues of alpha-aminoadipic-delta-semialdehyde. This posttranslational chemical change permits the covalent crosslinking of the component chains of collagen and those of elastin, thus stabilizing the fibrous deposits of these proteins in the extracellular matrix. Four LOX-like (LOXL) proteins with varying degrees of similarity to LOX have been described, constituting a family of related proteins. LOX is synthesized as a preproprotein which emerges from the cell as proLOX and then is processed to the active enzyme by proteolysis. In addition to elastin and collagen, LOX can oxidize lysine within a variety of cationic proteins, suggesting that its functions extend beyond its role in the stabilization of the extracellular matrix. Indeed, recent findings reveal that LOX and LOXL proteins markedly influence cell behavior including chemotactic responses, proliferation, and shifts between the normal and malignant phenotypes.

Function and structure of the molybdenum cofactor carrier protein from Chlamydomonas reinhardtii

The molybdenum cofactor (Moco) forms the catalytic site in all eukaryotic molybdenum enzymes and is synthesized by a multistep biosynthetic pathway. The mechanism of transfer, storage, and insertion of Moco into the appropriate apo-enzyme is poorly understood. In Chlamydomonas reinhardtii, a Moco carrier protein (MCP) has been identified and characterized recently. Here we show biochemical evidence that MCP binds Moco as well as the tungstate-substituted form of the cofactor (Wco) with high affinity, whereas molybdopterin, the ultimate cofactor precursor, is not bound. This binding selectivity points to a specific metal-mediated interaction with MCP, which protects Moco and Wco from oxidation with t((1/2)) of 24 and 96 h, respectively. UV-visible spectroscopy showed defined absorption bands at 393, 470, and 570 nm pointing to ene-diothiolate and protein side-chain charge transfer bonds with molybdenum. We have determined the crystal structure of MCP at 1.6 Angstrom resolution using seleno-methionated and native protein. The monomer constitutes a Rossmann fold with two homodimers forming a symmetrical tetramer in solution. Based on conserved surface residues, charge distribution, shape, in silico docking studies, structural comparisons, and identification of an anionbinding site, a prominent surface depression was proposed as a Moco-binding site, which was confirmed by structure-guided mutagenesis coupled to substrate binding studies.

Molybdenum cofactor biosynthesis and deficiency

The molybdenum cofactor (Moco) forms the active site of all molybdenum (Mo) enzymes, except nitrogenase. Mo enzymes catalyze important redox reactions in global metabolic cycles. Moco consists of Mo covalently bound to one or two dithiolates attached to a unique tricyclic pterin moiety commonly referred to as molybdopterin (MPT). Moco is synthesized by an ancient and conserved biosynthetic pathway that can be divided into four steps, according to the biosynthetic intermediates precursor Z (cyclic pyranopterin monophosphate), MPT and adenylated MPT. In a fifth step modifications such as attachment of nucleotides, sulfuration or bond formation between Mo and the protein result in different catalytic Mo centers. A defect in any of the steps of Moco biosynthesis results in the pleiotropic loss of all Mo enzyme activities. Human Moco deficiency is a hereditary metabolic disorder characterized by severe neurodegeneration resulting in early childhood death. Recently, a first substitution therapy was established.

The Bean pod mottle virus proteinase cofactor and putative helicase are symptom severity determinants

Full-length infectious cDNA clones were constructed from the genomic RNAs of three distinct strains (K-G7, K-Ha1 and K-Ho1) of the comovirus Bean pod mottle virus (BPMV). Whereas K-G7, a subgroup I strain, and K-Ha1, a subgroup II strain produce mild mottling, the reassortant strain K-Ho1 (RNA1(I) + RNA2(II)) induces necrotic primary lesions on inoculated leaves of soybean and severe systemic leaf mottling and blistering. Pseudorecombinants of all possible combinations of transcripts were generated and tested for symptom production. Only soybean plants inoculated with combinations having RNA1 derived from the severe strain K-Ho1, regardless of the origin of RNA2, induced severe symptoms, indicating that symptom severity maps to RNA1. Experiments with chimeric RNA1 constructs indicated that the coding regions of the protease co-factor (Co-pro) and the C-terminal half of the putative helicase (Hel) are determinants of symptom severity. Symptom severity correlated well with higher accumulation of viral RNA, but neither the Co-pro nor Hel protein could be demonstrated as a suppressor of RNA silencing.

Characterization of a thermostable recombinant beta-galactosidase from Thermotoga maritima

AIMS

Characterization of a thermostable recombinant beta-galactosidase from Thermotoga maritima for the hydrolysis of lactose and the production of galacto-oligosaccharides.

METHODS AND RESULTS

A putative beta-galactosidase gene of Thermotoga maritima was expressed in Escherichia coli as a carboxyl terminal His-tagged recombinant enzyme. The gene encoded a 1100-amino acid protein with a calculated molecular weight of 129,501. The expressed enzyme was purified by heat treatment, His-tag affinity chromatography, and gel filtration. The optimum temperatures for beta-galactosidase activity were 85 and 80 degrees C with oNPG and lactose, respectively. The optimum pH value was 6.5 for both oNPG and lactose. In thermostability experiments, the enzyme followed first-order kinetics of thermal inactivation and its half-life times at 80 and 90 degrees C were 16 h and 16 min, respectively. Mn2+ was the most effective divalent cation for beta-galactosidase activity on both oNPG and lactose. The Km and Vmax values of the thermostable enzyme for oNPG at 80 degrees C were 0.33 mm and 79.6 micromol oNP min(-1) mg(-1). For lactose, the Km and Vmax values were dependent on substrate concentrations; 1.6 and 63.3 at lower concentrations up to 10 mm of lactose and 27.8 mm and 139 micromol glucose min(-1) mg(-1) at higher concentrations, respectively. The enzyme displayed non-Michaelis-Menten reaction kinetics with substrate activation, which was explained by simultaneous reactions of hydrolysis and transgalactosylation.

CONCLUSIONS

The results suggest that the thermostable enzyme may be suitable for both the hydrolysis of lactose and the production of galacto-oligosaccharides.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of this work contribute to the knowledge of hydrolysis and transgalactosylation performed by beta-galactosidase of hyperthermophilic bacteria.

Tetrahydrobiopterin increases insulin sensitivity in patients with type 2 diabetes and coronary heart disease

Tetrahydrobiopterin (BH(4)) is an essential cofactor of nitric oxide synthase that improves endothelial function in diabetics, smokers, and patients with hypercholesterolemia. Insulin resistance has been suggested as a contributing factor in the development of endothelial dysfunction via an abnormal pteridine metabolism. We hypothesized that BH(4) would restore flow-mediated vasodilation (FMD, endothelial-dependent vasodilation), which may affect insulin resistance in type 2 diabetic patients. Thirty-two subjects (12 type 2 diabetic subjects, 10 matched nondiabetic subjects, and 10 healthy unmatched subjects) underwent infusion of BH(4) or saline in a random crossover study. Insulin sensitivity index (S(I)) was measured by hyperinsulinemic isoglycemic clamp. FMD was measured using ultrasonography. BH(4) significantly increased S(I) in the type 2 diabetics [3.6 +/- 0.6 vs. 4.9 +/- 0.7 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P < 0.05], while having no effects in nondiabetics [8.9 +/- 1.1 vs. 9.0 +/- 0.9 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P = 0.92] or in healthy subjects [17.5 +/- 1.6 vs. 18 +/- 1.8 x 10(-4) dl.kg(-1).min(-1)/(microU/ml), P = 0.87]. BH(4) did not affect the relative changes in brachial artery diameter from baseline FMD (%) in type 2 diabetic subjects (2.3 +/- 0.8 vs. 1.8 +/- 1.0%, P = 0.42), nondiabetic subjects (5.3 +/- 1.1 vs. 6.6 +/- 0.9%, P = 0.32), or healthy subjects (11.9 +/- 0.6 vs. 11.0 +/- 1.0%, P = 0.48). In conclusion, BH(4) significantly increases insulin sensitivity in type 2 diabetic patients without any discernible improvement in endothelial function.

The Redox Behavior of the Heme in Cystathionine β-synthase Is Sensitive to pH

Human cystathionine beta-synthase (CBS) is a unique pyridoxal-5'-phosphate-dependent enzyme in which heme is also present as a cofactor. Because the function of heme in this enzyme has yet to be elucidated, the study presented herein investigated possible relationships between the chemistry of the heme and the strong pH dependence of CBS activity. This study revealed, via study of a truncation variant, that the catalytic core of the enzyme governs the pH dependence of the activity. The heme moiety was found to play no discernible role in regulating CBS enzyme activity by sensing changes in pH, because the coordination sphere of the heme is not altered by changes in pH over a range of pH 6-9. Instead, pH was found to control the equilibrium amount of ferric and ferrous heme present after reaction of CBS with one-electron reducing agents. A variety of spectroscopic techniques, including resonance Raman, magnetic circular dichroism, and electron paramagnetic resonance, demonstrated that at pH 9 Fe(II) CBS is dominant while at pH 6 Fe(III) CBS is favored. At low pH, Fe(II) CBS forms transiently but reoxidizes by an apparent proton-gated electron-transfer mechanism. Regulation of CBS activity by the iron redox state has been proposed as the role of the heme moiety in this enzyme. Given that the redox behavior of the CBS heme appears to be controlled by pH, interplay of pH and oxidation state effects must occur if CBS activity is redox regulated.

Characterization of the cofactor-independent phosphoglycerate mutase from Leishmania mexicana mexicana. Histidines that coordinate the two metal ions in the active site show different susceptibilities to irreversible chemical modification

Phosphoglycerate mutase (PGAM) activity in promastigotes of the protozoan parasite Leishmania mexicana is found only in the cytosol. It corresponds to a cofactor-independent PGAM as it is not stimulated by 2,3-bisphosphoglycerate and is susceptible to EDTA and resistant to vanadate. We have cloned and sequenced the gene and developed a convenient bacterial expression system and a high-yield purification protocol. Kinetic properties of the bacterially produced protein have been determined (3-phosphoglycerate: K(m) = 0.27 +/- 0.02 mm, k(cat) = 434 +/- 54 s(-1); 2-phosphoglycerate: K(m) = 0.11 +/- 0.03 mm, k(cat) = 199 +/- 24 s(-1)). The activity is inhibited by phosphate but is resistant to Cl(-) and SO(4) (2-). Inactivation by EDTA is almost fully reversed by incubation with CoCl(2) but not with MnCl(2), FeSO(4), CuSO(4), NiCl(2) or ZnCl(2). Alkylation by diethyl pyrocarbonate resulted in irreversible inhibition, but saturating concentrations of substrate provided full protection. Kinetics of the inhibitory reaction showed the modification of a new group of essential residues only after removal of metal ions by EDTA. The modified residues were identified by MS analysis of peptides generated by trypsin digestion. Two substrate-protected histidines in the proximity of the active site were identified (His136, His467) and, unexpectedly, also a distant one (His160), suggesting a conformational change in its environment. Partial protection of His467 was observed by the addition of 25 micro m CoCl(2) to the EDTA treated enzyme but not of 125 micro m MnCl(2), suggesting that the latter metal ion cannot be accommodated in the active site of Leishmania PGAM.

Regulation of endothelial nitric oxide synthase by tetrahydrobiopterin in vascular disease

Nitric oxide (NO), produced by endothelial nitric oxide synthase (eNOS), is a key signaling molecule in vascular homeostasis. Loss of NO bioavailability due to reduced synthesis and increased scavenging by reactive oxygen species is a cardinal feature of endothelial dysfunction in vascular disease states. The pteridine cofactor tetrahydrobiopterin (BH4) has emerged as a critical determinant of eNOS activity: when BH4 availability is limiting, eNOS no longer produces NO but instead generates superoxide. In vascular disease states, there is oxidative degradation of BH4 by reactive oxygen species. However, augmentation of BH4 concentrations in vascular disease by pharmacological supplementation, by enhancement of its rate of de novo biosynthesis or by measures to reduce its oxidation, has been shown in experimental studies to enhance NO bioavailability. Thus, BH4 represents a potential therapeutic target in the regulation of eNOS function in vascular disease.

Increased endothelial tetrahydrobiopterin synthesis by targeted transgenic GTP-cyclohydrolase I overexpression reduces endothelial dysfunction and atherosclerosis in ApoE-knockout mice

OBJECTIVE

Increased production of reactive oxygen species and loss of endothelial nitric oxide (NO) bioactivity are key features of vascular disease states such as atherosclerosis. Tetrahydrobiopterin (BH4) is a required cofactor for NO synthesis by endothelial nitric oxide synthase (eNOS); pharmacologic studies suggest that reduced BH4 availability may be an important mediator of endothelial dysfunction in atherosclerosis. We aimed to investigate the importance of endothelial BH4 availability in atherosclerosis using a transgenic mouse model with endothelial-targeted overexpression of the rate-limiting enzyme in BH4 synthesis, GTP-cyclohydrolase I (GTPCH).

METHODS AND RESULTS

Transgenic mice were crossed into an ApoE knockout (ApoE-KO) background and fed a high-fat diet for 16 weeks. Compared with ApoE-KO controls, transgenic mice (ApoE-KO/GCH-Tg) had higher aortic BH4 levels, reduced endothelial superoxide production and eNOS uncoupling, increased cGMP levels, and preserved NO-mediated endothelium dependent vasorelaxations. Furthermore, aortic root atherosclerotic plaque was significantly reduced in ApoE-KO/GCH-Tg mice compared with ApoE-KO controls.

CONCLUSIONS

These findings indicate that BH4 availability is a critical determinant of eNOS regulation in atherosclerosis and is a rational therapeutic target to restore NO-mediated endothelial function and reduce disease progression.

The involvement of molybdenum in life

Quite extraordinarily molybdenum is an essential element in life for the uptake of nitrogen from both nitrogen gas and nitrate, yet it is a relatively rare heavy trace element. It also functions in a few extremely important oxygen-atom transfer reactions at low redox potential. This review poses the question "Why does life depend upon molybdenum?" The answer has to be based upon the availability of the element and on chemical superiority in carrying out the essential tasks. We illustrate here the peculiarities of molybdenum chemistry and how they have become part of certain enzymes. The uptake and incorporation of molybdenum are dependent on its availability, selective pumps, and carriers (chaperones), but 4.5 x 10(9) years ago molybdenum was not available when both tungsten and vanadium or even iron were possibly used in its place. While these possibilities are explored, they leave many unanswered questions concerning the selection today of molybdenum.

Coupling of histone deacetylation to NAD breakdown by the yeast silencing protein Sir2: Evidence for acetyl transfer from substrate to an NAD breakdown product

The Saccharomyces cerevisiae silencing protein Sir2 is the founding member of a universally conserved family of proteins that have been shown to possess NAD-dependent histone deacetylation and ADP-ribosylation activities. Here we show that histone deacetylation by Sir2 is coupled to cleavage of the high-energy bond that links the ADP-ribose moiety of NAD to nicotinamide. Analysis of the NAD cleavage products revealed the presence of nicotinamide, ADP-ribose, and a third product that appeared to be related to ADP-ribose. With the use of label transfer experiments, we show that the acetyl group in the histone substrate is transferred to this NAD breakdown product during deacetylation, forming a product that we conclude to be O-acetyl-ADP-ribose. Detection of this species strongly argues for obligate coupling of histone deacetylation to NAD breakdown by Sir2. We propose reaction mechanisms that could account for this coupling via acetyl-ADP-ribose formation. The unprecedented coupling of amide bond cleavage to cleavage of a high-energy bond raises the possibility that NAD breakdown by Sir2 plays an important role in silencing that is independent of its requirement for deacetylation.

[New aspects of vitamin and coenzyme research]

Vitamins are defined as essential organic micronutrients that are not synthesized by mammals. Coenzymes are defined as organic compounds with low molecular weight that are required to show enzyme activities by reversibly binding with their apoenzymes. Most of vitamins and coenzymes show various biofunctions besides their functions as vitamins and coenzymes. Accordingly, it is more appropriate to understand both as effective biofactors. Various retinoid derivatives synthesized bind to retinoid binding proteins to regulate gene expressions and show other biofunctions. Pyridoxal phosphate serves as an inhibitor of catepsins, and regulates the gene expression. Several novel built-in coenzymes such as topaquinone and lysyltyrosylquinone have been demonstrated in mammalian and microbial enzymes.

The biochemistry, physiology and genetics of PQQ and PQQ-containing enzymes

Pyrrolo-quinoline quinone (PQQ) is the non-covalently bound prosthetic group of many quinoproteins catalysing reactions in the periplasm of Gram-negative bacteria. Most of these involve the oxidation of alcohols or aldose sugars. PQQ is formed by fusion of glutamate and tyrosine, but details of the biosynthetic pathway are not known; a polypeptide precursor in the cytoplasm is probably involved, the completed PQQ being transported into the periplasm. In addition to the soluble methanol dehydrogenase of methylotrophs, there are three classes of alcohol dehydrogenases; type I is similar to methanol dehydrogenase; type II is a soluble quinohaemoprotein, having a C-terminal extension containing haem C; type III is similar but it has two additional subunits (one of which is a multihaem cytochrome c), bound in an unusual way to the periplasmic membrane. There are two types of glucose dehydrogenase; one is an atypical soluble quinoprotein which is probably not involved in energy transduction. The more widely distributed glucose dehydrogenases are integral membrane proteins, bound to the membrane by transmembrane helices at the N-terminus. The structures of the catalytic domains of type III alcohol dehydrogenase and membrane glucose dehydrogenase have been modelled successfully on the methanol dehydrogenase structure (determined by X-ray crystallography). Their mechanisms are likely to be similar in many ways and probably always involve a calcium ion (or other divalent cation) at the active site. The electron transport chains involving the soluble alcohol dehydrogenases usually consist only of soluble c-type cytochromes and the appropriate terminal oxidases. The membrane-bound quinohaemoprotein alcohol dehydrogenases pass electrons to membrane ubiquinone which is then oxidized directly by ubiquinol oxidases. The electron acceptor for membrane glucose dehydrogenase is ubiquinone which is subsequently oxidized directly by ubiquinol oxidases or by electron transfer chains involving cytochrome bc1, cytochrome c and cytochrome c oxidases. The function of most of these systems is to produce energy for growth on alcohol or aldose substrates, but there is some debate about the function of glucose dehydrogenases in those bacteria which contain one or more alternative pathways for glucose utilization. Synthesis of the quinoprotein respiratory systems requires production of PQQ, haem and the dehydrogenase subunits, transport of these into the periplasm, and incorporation together with divalent cations, into active quinoproteins and quinohaemoproteins. Six genes required for regulation of synthesis of methanol dehydrogenase have been identified in Methylobacterium, and there is evidence that two, two-component regulatory systems are involved.

Purification and characterization of NADPH-cytochrome P450 reductase from filamentous fungus Rhizopus nigricans

We report here the isolation and partial characterization of a flavoprotein, NADPH-cytochrome P450 (cytochrome c) reductase. The enzyme is a part of steroid 11 alpha-hydroxylating system and is associated with the microsomal fraction of the fungus Rhizopus nigricans. Fungal reductase was solubilized from microsomal membranes with Triton X-100 and purified to apparent homogeneity by affinity and high-performance ion-exchange chromatography. A 350-fold purification of the enzyme with specific activity of 37 mumol cytochrome c reduced/min/mg protein was achieved. A single protein band was obtained on SDS-PAGE analysis with an apparent molecular weight of 79 kDa. Purified reductase contained approximately equimolar quantities of flavin adenine dinucleotide and flavin mononucleotide per mole of the enzyme. Upon induction of the steroid hydroxylating system with progesterone the activity of microsomal NADPH-cytochrome c (P450) reductase increased 10-fold. This is in good correlation with the increase in content of fungal cytochrome P450. Purified fungal flavoprotein was active in a reconstituted system with cytochrome P450 C21 from adrenal gland but could not replace adrenodoxin reductase in the mitochondrial steroid 11 beta-hydroxylating system. We were able to confirm the role of the enzyme by reconstituting steroid 11 alpha-hydroxylating activity from the separated components NADPH-cytochrome P450 reductase and cytochrome P450, partly purified from fungal microsomes.

Catalytic significance of the specificity of divalent cations as KS* and kcat* cofactors for secreted phospholipase A2

Calcium is required for the substrate binding and for the chemical step of the interfacial catalytic turnover cycle of pancreatic phospholipase A2 (PLA2), but not for the binding of the enzyme to the interface. The role of calcium and other divalent cations (C) is analyzed for the effect on the substrate binding and kcat* for the chemical step. The cofactor role of 3d-cations(II) (C) for the hydrolysis of dimyristoylphosphatidylmethanol (DMPM) vesicles is characterized as an equilibrium dissociation constant for the interfacial binary (E*C) and ternary (E*CL) complexes of PLA2 and substrate mimics (L). Of the cations(II) that promote the binding of a mimic to the enzyme at the interface (E*), only a subgroup supports the chemical step. For example, Cd, Zn, and Cu form ternary E*CL complexes with kcat* of <1 s-1, compared to the rate of >100 s-1 with Ca, Fe, Mn, Co, and Ni. Oxygen exchange from H218O to the products of hydrolysis of DMPM incorporates one 18O in myristate. Incorporation of the first and second 18O occurs during the incubation of both the products of hydrolysis in H218O with PLA2 and Ca, but not with Zn. The cation-dependent changes in the UV difference spectrum, associated with the formation of E*C and E*CL, suggest that the changes are mainly due to catalytic His-48, and possibly Tyr-52 and Tyr-73, and are different with Ca as opposed to Zn. These results and simulations suggest considerable plasticity in the calcium binding and catalytic site environment. It is proposed that the higher ground state stability of the E*CS complex with the inhibitory cations increases the effective activation energy. For the chemical step, calcium coordinated with a nucleophilic water and the ester carbonyl oxygen facilitates the near-attack geometry in the E*CaS, and the His-48.Asp-99 pair acts as a proton acceptor. As a prelude to establishing the catalytic mechanism, factors controlling the energetically demanding transition state are also discussed.

p47 is a cofactor for p97-mediated membrane fusion

At least two distinct ATPases, NSF and p97, are known to be involved in the heterotypic fusion of transport vesicles with their target membranes and the homotypic fusion of membrane compartments. The NSF-mediated fusion pathway is the best characterized, many of the components having been identified and their functions analysed. In contrast, none of the accessory proteins for the p97-mediated fusion pathway has been identified. Now we have identified the first such component, a protein of relative molecular mass 47,000 (p47), which forms a tight, stoichiometric complex with cytosolic p97 (one trimer of p47 per hexamer of p97). It is essential for the p97-mediated regrowth of Golgi cisternae from mitotic Golgi fragments, a process restricted to animal cells. As a homologue of p47 exists in budding yeast, this indicates that it might also be involved in other membrane fusion reactions catalysed by p97, such as karyogamy.

Effects of ethanol on the levels of brain 6R-L-erythro-5, 6, 7, 8-tetrahydrobiopterin in the inbred strains of mice. DBA/2J, C3H/HeJ and C57BL/6J with different alcohol preferences

6R-L-erythro-5, 6, 7, 8-tetrahydrobiopterin (6R-BH4) is a coenzyme for tyrosine, tryptophan and phenylalanine hydroxylases, the former two of which are the initial and the rate-limiting enzymes in the biosynthesis of the catecholamines and serotonin, respectively. The present study was designed to determine the changes in concentrations of 6R-BH4 in striatum and midbrain of the inbred strains of mice, DBA/2J, C3H/HeJ and C57BL/6J, with different genetically determined alcohol preferences, following the injection of ethanol (EtOH). The intraperitoneal administration of EtOH (0, 1, 2 and 4 g/kg) significantly and dose-dependently reduced the levels of striatal and midbrain 6R-BH4 in DBA/2J mice with the lowest alcohol preference, and EtOH (4 g/kg, i.p.) reduced the level of striatal 6R-BH4 in C3H/HeJ with medium alcohol preference. Following the administration of EtOH (4 g/kg, i.p.), brain 6R-BH4 levels in C57BL/6J mice with high alcohol preference were lowered compared with the control group, but the difference did not reach statistic significance. EtOH has a tendency to reduce the brain 6R-BH4 levels in mice with lower alcohol preference or higher sensitivity to EtOH. Based on these findings, it was proposed that differences in alcohol drinking behavior in the inbred strains of mice was influenced by brain 6R-BH4.