Minimal residual disease detection by next-generation sequencing in multiple myeloma: Promise and challenges for response-adapted therapy

Assessment of minimal residual disease (MRD) is becoming a standard diagnostic tool for curable hematological malignancies such as chronic and acute myeloid leukemia. Multiple myeloma (MM) remains an incurable disease, as a major portion of patients even in complete response eventually relapse, suggesting that residual disease remains. Over the past decade, the treatment landscape of MM has radically changed with the introduction of new effective drugs and the availability of immunotherapy, including targeted antibodies and adoptive cell therapy. Therefore, conventional serological and morphological techniques have become suboptimal for the evaluation of depth of response. Recently, the International Myeloma Working Group (IMWG) introduced the definition of MRD negativity as the absence of clonal Plasma cells (PC) with a minimum sensitivity of <10⁻⁵ either by next-generation sequencing (NGS) using the LymphoSIGHT platform (Sequenta/Adaptative) or by next-generation flow cytometry (NGF) using EuroFlow approaches as the reference methods. While the definition of the LymphoSIGHT platform (Sequenta/Adaptive) as the standard method derives from its large use and validation in clinical studies on the prognostic value of NGS-based MRD, other commercially available options exist. Recently, the LymphoTrack assay has been evaluated in MM, demonstrating a sensitivity level of 10⁻⁵, hence qualifying as an alternative effective tool for MRD monitoring in MM. Here, we will review state-of-the-art methods for MRD assessment by NGS. We will summarize how MRD testing supports clinical trials as a useful tool in dynamic risk-adapted therapy. Finally, we will also discuss future promise and challenges of NGS-based MRD determination for clinical decision-making. In addition, we will present our real-life single-center experience with the commercially available NGS strategy LymphoTrack-MiSeq. Even with the limitation of a limited number of patients, our results confirm the LymphoTrack-MiSeq platform as a cost-effective, readily available, and standardized workflow with a sensitivity of 10⁻⁵. Our real-life data also confirm that achieving MRD negativity is an important prognostic factor in MM.

Live birth following a single oocyte fertilized with ICSI and embryo biopsy at blastocyst stage: a case report

In this report, we present a case of a couple who obtained a live birth with a single oocyte fertilized by ICSI. Two oocytes were collected at 35.5 hours (h) post trigger and both were at metaphase II when sperm injection was performed (38 h). At 18 h post injection, one oocyte was fertilized, developed to the blastocyst stage and underwent to trophectoderm biopsy for preimplantation genetic testing on day 5. Following biopsy, the blastocyst was vitrified and 4 h after warming procedure, the euploid blastocyst was replaced to the uterine cavity. Healthy live birth was obtained after 39 weeks of gestation.

Nutritional, antioxidant and sensory properties of functional beef burgers formulated with chia seeds and goji puree, before and after in vitro digestion

The addition of chia seeds and goji puree (2.5 and/or 5%) was evaluated in terms of their effects on the fatty acid profile, lipid peroxidation, total phenols and antioxidant capacity of cooked beef burgers. In comparison to control burgers, polyunsaturated fatty acids doubled or tripled in samples containing chia seeds; polyphenols and antioxidant capacities (ORAC, ABTS, DPPH) increased up to 70% and malondialdehyde values were reduced up to 50% in burgers formulated with both ingredients. Polyphenols, antioxidant capacity and lipid peroxidation were also assessed after in vitro digestion. A marked increase of polyphenol bioaccessibility and antioxidant capacity was observed for all samples, but also malondialdehyde values were increased after digestion, especially in samples containing 5% chia seeds. Finally, hedonistic tests were conducted on young (18-30 years), adult (31-60 years) and elderly (>60 years) subjects and the burgers resulted acceptable by all groups, appointing to their potential application as functional burgers.

A Combination of Moringin and Avenanthramide 2f Inhibits the Proliferation of Hep3B Liver Cancer Cells Inducing Intrinsic and Extrinsic Apoptosis

Moringin (MOR), a glycosyl-isothiocyanate obtained by myrosinase-catalyzed hydrolysis of the precursor 4-(α-l-rhamnosyloxy)-benzyl glucosinolate (glucomoringin), found predominantly in the seeds of Moringa oleifera, shows anticancer effects against several cancer cell lines. Avenanthramide (AVN) 2f is a phytochemical purified from oats with antioxidant and anticancer properties. The aim of this study was to investigate the antiproliferative and proapoptotic effects of MOR and AVN 2f used alone and in combination on Hep3B cancer cells, which are highly resistant to conventional anticancer drugs. We found that a cocktail of MOR and AVN 2f significantly inhibited the Hep3B proliferation rate by markedly increasing the activity of caspases 2, 8, 9, and 3. Extrinsic apoptosis was induced by the AVN 2f-mediated activation of caspase 8, while the intrinsic apoptotic pathway was triggered by MOR-induced increase in the levels of intracellular reactive oxygen species, MOR-mediated activation of caspases 2 and 9 and the MOR-mediated downregulation of the prosurvival gene BIRC5. Our results suggest that the combination MOR + AVN 2f could be an effective chemopreventive cocktail against the development of hepatocarcinoma.

Novel insights into pericarp, protein body globoids of aleurone layer, starchy granules of three cereals gained using atomic force microscopy and environmental scanning electronic microscopy

In this study, we applied Environmental Scanning Electron Microscopy-Energy Dispersive Spectroscopy (ESEM-EDS) and Atomic Force Microscopy (AFM) analysis to three different cereal caryopses: barley, oat and einkorn wheat. The morphological structures, chemical elemental composition and surface characteristics of the three cereals were described. Regarding the morphology, barley showed the thickest pericarp, providing a strong barrier digestion and absorption of nutrients. The aleurone layer of each cereal type contained protein body globoids within its cells. Large type-A and small type-B starchy granules were revealed in the endosperm of barley and einkorn wheat, whereas irregular starchy granules were found in oats. The starchy granule elemental composition, detected by ESEM-EDS, was rather homogenous in the three cereals, whereas the pericarp and protein body globoids showed heterogeneity. In the protein body globoids, oats showed higher P and K concentrations than barley and einkorn wheat. Regarding the topographic profiles, detected by AFM, einkorn wheat starchy granules showed a surface profile that differed significantly from that of oats and barley, which were quite similar to one another. The present work provides insights into the morphological and chemical makeup of the three grains shedding light on the higher bio-accessibility of einkorn wheat nutrients compared to barley and oats, providing important suggestions for human nutrition and technological standpoints.

Betacyanins enhance vitexin-2-O-xyloside mediated inhibition of proliferation of T24 bladder cancer cells

Betacyanins (BC) were purified from beetroot (Beta vulgaris var. rubra L.) and tested, alone or in combination with vitexin-2-O-xyloside (XVX) from Beta vulgaris var. cicla L., for their ability to reduce the proliferation rate in T24 bladder cancer cells. Combination of BC and XVX exhibited a synergistic effect concerning the inhibition of proliferation in T24 cancer cells at 24 and 48 h but not after 72 h of incubation. The induction of apoptosis was evidenced by means of fluorescence activated cell sorting (FACS) analysis, as well as through the increase in caspase 3 and 8 activities. Using RTqPCR experiments, it was shown that the combination of XVX + BC was able to enhance the expression levels of pro-apoptotic BAX and downregulate anti-apoptotic BIRC5 (survivin), as well as pro-survival CTNNB1 (β-catenin). The most evident effect of BC was the increase of the activity of caspase 8, leading to induction of extrinsic apoptosis. Moreover, XVX, BC and their combination showed no cytotoxic effect on normal human skin NCTC 2544 keratinocytes. These results demonstrated the efficacy and the mechanisms of the action of BC and XVX, extracted from edible plants, and suggested that a diet or a nutrition supplement, enriched with these bioactive molecules, could be used in the prevention of human bladder cancer.

Natural and synthetic avenanthramides activate caspases 2, 8, 3 and downregulate hTERT, MDR1 and COX-2 genes in CaCo-2 and Hep3B cancer cells

Avenanthramides inhibit proliferation of CaCo-2 and Hep3B cancer cells through induction of apoptosis and downregulation of pro-survival mechanisms.

The effect of mechanical processing on avenanthramide and phenol levels in two organically grown Italian oat cultivars

Avenanthramides (AVNs), free and bound phenols and their antioxidant capacities (ORAC) were evaluated in two Avena sativa L. cultivars, Donata and Flavia. The cultivars (cvs.) were grown in loamy and medium texture soils and assessed after industrial dehulling and milling. Total dietary fiber, β-glucan, starch and proteins were also evaluated. Cv. Donata showed 2.8 fold higher AVN storage as compared to cv. Flavia, which was linked with genotype. The accumulation of AVN content was also influenced by the texture of the soil. Dehulling resulted in a 75 and 37% AVN decrease in cv. Donata and Flavia, respectively. The dehulled grains of cv. Donata showed 40% reduction in free phenolic content, whereas the dehulled grains of both cvs. showed 67% reduction in bound phenols. Milling affected the bound phenolics and their antioxidant capacity. Cv. Flavia showed 1.3 fold higher β-glucan than that of cv. Donata. Total dietary fiber was reduced by 50 and 12% after dehulling and milling, respectively, while marginal changes in proteins were observed after milling. The results suggest that the choice of genotype and the kind of dehulling processes that are employed are essential considerations in the production of oat-based products with high AVN content and extra health benefits.

C-Glycosyl Flavonoids from Beta vulgaris Cicla and Betalains from Beta vulgaris rubra: Antioxidant, Anticancer and Antiinflammatory Activities-A Review

The green beet (Beta vulgaris var. cicla L.) and red beetroot (B. vulgaris var. rubra L.) contain phytochemicals that have beneficial effects on human health. Specifically, the green beet contains apigenin, vitexin, vitexin-2-O-xyloside and vitexin-2-O-rhamnoside, while the red beetroot is a source of betaxanthins and betacyanins. These phytochemicals show considerable antioxidant activity, as well as antiinflammatory and antiproliferative activities. Vitexin-2-O-xyloside, in combination with betaxanthins and betacyanins, exerts antiproliferative activity in breast, liver, colon and bladder cancer cell lines, through the induction of both intrinsic and extrinsic apoptotic pathways. A significant body of evidence also points to the role of these phytochemicals in the downregulation of the pro-survival genes, baculoviral inhibitor of apoptosis repeat-containing 5 and catenin beta-1, as well as the genes controlling angiogenesis, hypoxia inducible factor 1A and vascular endothelial growth factor A. The multi-target action of these phytochemicals enhances their anticancer activity. Vitexin-2-O-xyloside, betaxanthins and betacyanins can be used in combination with conventional anticancer drugs to reduce their toxicity and overcome the multidrug resistance of cancer cells. In this review, we describe the molecular mechanisms that enable these dietary phytochemicals to block the proliferation of tumor cells and inhibit their pro-survival pathways. Copyright © 2017 John Wiley & Sons, Ltd.

Histone demethylase JARID1C inactivation triggers genomic instability in sporadic renal cancer

Mutations in genes encoding chromatin-remodeling proteins are often identified in a variety of cancers. For example, the histone demethylase JARID1C is frequently inactivated in patients with clear cell renal cell carcinoma (ccRCC); however, it is largely unknown how JARID1C dysfunction promotes cancer. Here, we determined that JARID1C binds broadly to chromatin domains characterized by the trimethylation of lysine 9 (H3K9me3), which is a histone mark enriched in heterochromatin. Moreover, we found that JARID1C localizes on heterochromatin, is required for heterochromatin replication, and forms a complex with established players of heterochromatin assembly, including SUV39H1 and HP1α, as well as with proteins not previously associated with heterochromatin assembly, such as the cullin 4 (CUL4) complex adaptor protein DDB1. Transcription on heterochromatin is tightly suppressed to safeguard the genome, and in ccRCC cells, JARID1C inactivation led to the unrestrained expression of heterochromatic noncoding RNAs (ncRNAs) that in turn triggered genomic instability. Moreover, ccRCC patients harboring JARID1C mutations exhibited aberrant ncRNA expression and increased genomic rearrangements compared with ccRCC patients with tumors endowed with other genetic lesions. Together, these data suggest that inactivation of JARID1C in renal cancer leads to heterochromatin disruption, genomic rearrangement, and aggressive ccRCCs. Moreover, our results shed light on a mechanism that underlies genomic instability in sporadic cancers.

H3K4me3 demethylation by the histone demethylase KDM5C/JARID1C promotes DNA replication origin firing

DNA replication is a tightly regulated process that initiates from multiple replication origins and leads to the faithful transmission of the genetic material. For proper DNA replication, the chromatin surrounding origins needs to be remodeled. However, remarkably little is known on which epigenetic changes are required to allow the firing of replication origins. Here, we show that the histone demethylase KDM5C/JARID1C is required for proper DNA replication at early origins. JARID1C dictates the assembly of the pre-initiation complex, driving the binding to chromatin of the pre-initiation proteins CDC45 and PCNA, through the demethylation of the histone mark H3K4me3. Fork activation and histone H4 acetylation, additional early events involved in DNA replication, are not affected by JARID1C downregulation. All together, these data point to a prominent role for JARID1C in a specific phase of DNA replication in mammalian cells, through its demethylase activity on H3K4me3.

Targeting Mcl-1 for multiple myeloma (MM) therapy: drug-induced generation of Mcl-1 fragment Mcl-1(128-350) triggers MM cell death via c-Jun upregulation

Myeloid cell leukemia-1 (Mcl-1, HGNC: 6943), a pro-survival member of the Bcl-2 family, plays a crucial role in Multiple Myeloma (MM) pathogenesis and drug resistance, thus representing a promising therapeutic target in MM. A novel strategy to inhibit Mcl-1 activity is the induction of ubiquitin-independent Mcl-1 degradation. Our own and other previous studies have demonstrated caspase-dependent generation of a 28kDa Mcl-1 fragment, Mcl-1(128-350), which inhibits MM cell proliferation and survival. Here, we show that similar to bortezomib, the novel proteasome inhibitors carfilzomib and ixazomib, as well as staurosporine and adaphostin, induce the generation of Mcl-1(128-350) in MM cells. Next, the molecular sequelae downstream of Mcl-1(128-350), which mediate its pro-apoptotic activity, were delineated. Surprisingly, we observed nuclear accumulation of drug-induced or exogenously overexpressed Mcl-1(128-350), followed by elevated mRNA and protein levels of c-Jun, as well as enhanced AP-1 reporter activity. Moreover, drug-induced AP-1 activity was blocked after introducing a point mutation into the highly conserved Mcl-1 caspase-cleavage site Asp127, but not Asp157. Consequently, drug-triggered cell death was significantly decreased in MM cells transfected with Mcl-1 D127A, but not with Mcl-1 D157A. Consistent with these data, treatment with bortezomib triggered c-Jun upregulation followed by apoptosis in Mcl-1(wt/wt), but not Mcl-1(Δ/null) murine embryonic fibroblasts (MEFs). Transfection of a plasmid carrying Mcl-1(wt) into Mcl-1(Δ/null) MEFs restored bortezomib-induced Mcl-1 fragmentation, c-Jun upregulation and AP-1 reporter activity. Finally, our data indicate that drug-induced generation of a pro-apoptotic Mcl-1 fragment followed by c-Jun upregulation may also be a novel therapeutic approach in other tumor entities.

Heart failure in community-dwelling older persons: aims, design and adherence rate of the ICARe Dicomano project: an epidemiologic study. Insufficienza Cardiaca negli Anziani Residenti a Dicomano

BACKGROUND

The prevalence of heart failure (HF) increases with age, and HF is a major cause of disability and mortality in older persons. Detection of HF in epidemiological studies has relied on criteria validated only in young and middle-age adults, and, therefore, may prove inadequate in older subjects, because they do not take into account the pathophysiologic and clinical peculiarities of HF in old age. Thus, the true prevalence of HF in the older general population remains uncertain and has probably been underestimated in previous studies. Moreover, the mechanism and the extent by which HF hinders physical functioning in older people has not been fully elucidated.

OBJECTIVES

This paper describes the design of the ICARe study, carried out in an older home-dwelling population to collect data about: (1) the sensitivity and specificity of diagnostic criteria used previously in epidemiological studies of HF; (2) the prevalence of the different pathophysiologic forms of HF; and (3) the impact of HF on overall health status, and on physical functioning, in the absence or presence of chronic comorbidity.

DESIGN AND SETTING

This was a cross-sectional survey. Eligible were all community-dwelling persons aged 65 years or older recorded in the Registry Office of Dicomano, a small town nearby Florence (Italy). All the domains of multidimensional geriatric assessment were explored through different phases of the study (home interview, laboratory testing, geriatric visit) that comprised an extensive cardiopulmonary instrumental assessment including: color Doppler echocardiography, echotomography of the carotid arteries used in an original method to determine arterial compliance, and bell spirometry. Presence of major chronic conditions was ascertained by predefined, standard algorithms that were based largely on clinical examination.

RESULTS

There were 864 older persons eligible for the ICARe study. Even with a substantial decline from home interview (91.2%) to the cardiopulmonary study (71.1%), the adherence rate remained high throughout the study, and the population examined was fairly representative of the original eligible population. Thus, we believe that the data collected in this study offer a unique opportunity to assess the validity of the diagnostic clinical criteria for HF in the general older population, to identify the pathophysiology underlying the syndrome, and to investigate the relationship between HF, comorbidity, and disability.

[Guideline for the prevention of sexually transmitted diseases in adolescents (University of Florence, Pediatric Department)]

Adolescent had in the past rarely been affected by sexually transmitted infections. Nowadays they must be considered possibly running such risks as they begin their sexual activity earlier or do not know enough about these kinds of troubles. Therefore a valid primary prevention is necessary based upon correct information.

Value of combined assessment of physical health and functional status in community-dwelling aged: a prospective study in Florence, Italy

A survey of the health and social conditions of a representative sample of 967 persons aged 60 years and older from the city of Florence, Italy, was undertaken in 1980. In 1987, a follow-up survey of this cohort was performed. There were 391 documented deaths, 408 survivors, and 168 individuals who could not be located. Functional ability at baseline was assessed using a World Health Organization 14-item scale. Indicators of physical health status included chronic disease status, number of drugs, physician visits, and days of hospitalization. After adjustment for age and sex, both functional ability and indicators of physical health status were found to be independent, statistically significant predictors of mortality. The results of this study further support the view that biomedical and functional assessment are both necessary for a comprehensive evaluation of the older population.

The effect of saturation with Zn2+ and other metal ions on the antibacterial activity of ovotransferrin

The antibacterial activity of metal complexes of ovotransferrin was tested "in vitro" against different bacterial species and the Zn2+ saturated ovotransferrin appeared to be the most active by comparison with the apo-protein and other metal complexes. Appropriate controls showed that such an effect was neither due to Zn2+ ions, nor to iron deprivation, but to a specific activity of the Zn-ovotransferrin complex. This antibacterial activity required a direct contact of Zn-ovotransferrin with the bacterial surface. In vivo experiments confirmed the higher antibacterial activity of Zn-ovotransferrin as compared with the apo-form.

Calorimetric studies of oxyhemoglobin dissociation. II. Erythrocytic oxygen depletion by sodium dithionite

Dithionite causes the depletion of dioxygen from suspensions of erythrocytes by reduction of the external dioxygen and not by diffusion into the cell. The molar enthalpy for the reduction shows a small difference with respect to the values found for free hemoglobin; and the normal stoichiometry of 2 moles dithionite/mole dioxygen found there is not observed with erythrocytes. At low hematocrit, the stoichiometry is 2.6:1 and decreases to 1.5:1 at high hematocrit. The change is not due to differences in the hemoglobin saturation or to an inability of dithionite to reduce all dioxygen present at the higher hematocrit. Neither catalase nor peroxidase added to the extracellular volume significantly alters the stoichiometry or the enthalpy of dioxygen reduction by dithionite. Addition of superoxide dismutase, however, restores the normal stoichiometry at high hematocrit and further increases the stoichiometry at low hematocrit. The calorimetrical signal of hydrogen peroxide, clearly seen with free dioxygen, is not present with erythrocytes. In all these cases the total heat evolved is the same.

Redox potentials of normal and SH(beta 93)-modified human hemoglobin. Effect of pH and D-glycerate 2,3-bisphosphate

The effect of pH and D-glycerate 2,3-bisphosphate on the oxidation-reduction equilibria of human hemoglobin, normal and modified at the SH(beta 93) groups by reaction with cystine dimethylester has been studied with the aim of comparing the redox equilibria with the oxygen equilibria previously studied under the same experimental conditions. Analysis of data has shown that: (i) the same groups are involved in the oxygenation and oxidation alkaline Bohr effect; (ii) the pK values of these groups are lower in met-hemoglobin than in oxyhemoglobin; (iii) the difference in the affinity for D-glycerate 2,3-bisphosphate of ferric and deoxyhemoglobin is pH-independent in the normal protein, while significantly decreasing with a decrease in pH in the modified protein; (iv) the high cooperativity of the redox process (also occurring at acid pH) and the reduced oxidation Bohr effect observed in the modified protein are consistent with the destabilization of the T structure induced by the bulky reagent bound to the SH(beta 93) groups of the protein.

Kinetics of ligand binding and quaternary conformational change in the homodimeric hemoglobin from Scapharca inaequivalvis

The kinetics of the reaction with oxygen and carbon monoxide of the homodimeric hemoglobin from the bivalve mollusc Scapharca inaequivalvis has been extensively investigated by flash and dye-laser photolysis, temperature jump relaxation, and stopped flow methods. The results indicate that cooperativity in ligand binding, already observed for oxygen at equilibrium, finds its kinetic counterpart in a large decrease of the oxygen dissociation velocity in the second step of the binding reaction. In the case of carbon monoxide, cooperativity is clearly evident in the increase of the combination velocity constant as the reaction proceeds. Therefore, the ligand-binding kinetics of this dimeric hemoglobin shows the characteristic features of the corresponding reactions of tetrameric hemoglobins. Analysis of the data in terms of the allosteric model proposed by Monod et al. (Monod, J., Wyman, J., and Changeux, J. P. (1965) J. Mol. Biol. 12, 88-118) has shown that the values of the allosteric parameters cannot be fixed uniquely for a dimeric hemoglobin. The rapid changes in absorbance observed at the isosbestic points of unliganded and liganded hemoglobin following laser photolysis provided a value of 7 X 10(4) S-1 at 20 degrees C for the rate of the ligand-free quarternary conformational change, postulated on the basis of cooperative ligand binding. Comparison of the rapid absorbance changes observed during ligand rebinding in this hemoglobin with those observed in tuna hemoglobin indicate that, at full photolysis, binding to the T state is followed by further binding and conversion to the liganded R state; at partial photolysis, population of the liganded T state occurs immediately and is followed by a decay to the liganded R state upon further ligand binding. These new results, in conjunction with previous equilibrium data on the same system, show unequivocally that the presence of two different types of chain is not an absolute prerequisite for cooperativity in hemoglobins, contrary to currently accepted ideas.

The pH dependence of pre-steady-state and steady-state kinetics for the porcine pancreatic β-kallikrein-B-catalyzed hydrolysis of p-nitrophenyl ester

Pre-steady-state and steady-state kinetics of the porcine pancreatic beta-kallikrein-B (EC 3.4.21.35) catalyzed hydrolysis of ZArgONp have been determined between pH 2.4 and 8. The results are consistent with a minimum three-step mechanism involving an acyl-enzyme intermediate: (see formula). The formation of the E X S complex may be regarded as a pseudoequilibrium process; the minimum values for k+1 are 5.9 X 10(6) M-1 X s-1 (pH 5.5) and 9.4 X 10(5) M-1 X s-1 (pH 2.4) and that for k-1 is 600 s-1. The value of k-1/k+1 (= Ks) changes from 102 microM at pH greater than or equal to 5.5 to 638 microM at pH less than 2.4. The pH dependence of k+2 conforms to two ionizing groups, in the E X S complex, with pKa values of 3.4 +/- 0.1 and 7.05 +/- 0.10. The pH profile of k+2/Ks (= kcat/Km) reflects the ionization of two groups, in the free enzyme, with pKa values of 4.2 +/- 0.1 and 7.05 +/- 0.10. The pH dependence of k+3 implicates two ionizing groups in the deacylation step with pKa values of 4.6 +/- 0.1 and 7.0 +/- 0.1. At acid pH values (pH 2.4-4.4), k+3 is rate-limiting in catalysis, whereas for pH values higher than 4.4, k+2 becomes rate-limiting. The observed neutral and acid ionizations probably reflect the acid-base equilibrium of His-57 and Asp-189 involved in the central site of beta-kallikrein-B. The structural basis for the specificity and catalytic behaviour of this proteinase are discussed and a role for Ser-226 is pinpointed.

Effect of bepridil on the activity of cytochrome c oxidase in solution and in proteoliposomes

The interaction between bepridil and mitochondrial cytochrome c oxidase has been studied using the purified enzyme either in aqueous suspensions in the presence of detergents, or embedded into phospholipid vesicles. The investigation, systematically extended to nonactin and valinomycin for comparison, showed that: (a) valinomycin and nonactin induce similar changes in the visible absorption spectrum of cytochrome oxidase; these changes are quite different from those induced by bepridil. (b) The three compounds have an effect on the functional properties of purified, solubilized oxidase which may be related to binding. In particular, bepridil displays a complex pH-dependent effect which at concentrations below 50 microM results in a stimulation of the activity of approximately 30% starting with the oxidized resting enzyme. At variance with valinomycin and nonactin, the stimulatory effect is the same, within the errors, for the detergent-suspended, the vesicle-embedded and even the Keilin-Hartree particles. (c) In the case of detergent-suspended oxidase, the stimulatory effect of bepridil is also similar whether the enzyme is in the resting or in the pulsed state. If the oxidase is embedded into vesicles, however, the pulsed state is significantly more sensitive to bepridil than the resting one. These results are discussed in the light of the possible role assigned to pulsed oxidase in the regulation of the electron flux through the respiratory chain.

Catalytic and ligand binding properties of bovine trypsinogen and its complex with the effector dipeptide Ile-Val. A comparative study

Steady-state and pre-steady-state kinetic data for the trypsinogen catalyzed hydrolysis of a series of synthetic substrates (i.e. p-nitrophenyl esters of N-alpha-carbobenzoxy-L-amino acids) have been obtained as a function of pH (3.4-8). Moreover, the effect of ethylamine on the hydrolysis of a neutral substrate and benzamidine binding have been extensively studied. In order to obtain direct information on the transition of trypsinogen to a beta-trypsin-like structure, the role of the effector dipeptide Ile-Val on the catalytic and ligand binding properties of the zymogen has been investigated. Kinetic and thermodynamic data for beta-trypsin and alpha-chymotrypsin are also reported for the purpose of an homogeneous comparison of the various (pro)enzymes. Under all the experimental conditions, kinetic data for (pro)enzyme catalysis are consistent with the minimum three-step mechanism: (formula; see text) involving the acyl intermediate E X P. In the presence of Ile-Val dipeptide, trypsinogen assumes catalytic and ligand binding properties that are reminiscent of activated beta-trypsin. This is at variance with free trypsinogen, which shows a alpha-chymotrypsin-like behavior. The large differences in the results of kinetic and thermodynamic measurements for free trypsinogen, as compared to its binary adduct with Ile-Val, can be ascribed to the substantial differences in the two molecular species, which include the spatial orientation of Asp189.

Catalytic properties of porcine pancreatic elastase: a steady-state and pre-steady-state study

Pre-steady-state and steady-state kinetics for the p.p. elastase-catalysed hydrolysis of ZAlaONp, one of the most favourable substrates for this serine protease, have been studied between pH 4.0 and 8.0. The results are consistent with the minimum three-step mechanism: (formula; see text) Under pre-steady-state conditions, where [E0] much greater than [S0], the values of the dissociation constant of the E X S complex (Ks = k-1/k+1) and of the individual rate constants for the catalytic steps (k+2 and k+3) have been determined over the whole pH range explored. Under steady-state conditions, where [S0] much greater than [E0], the values of kcat and Km have been obtained over the same pH range. The pH profiles of k+2, k+3, k+2/Ks, kcat, kcat/Km reflect the ionization of a group, probably His57, with a pKa value of 6.85 +/- 0.10. The values of Ks and Km are pH independent. The steady-state parameters for the p.p. elastase-catalysed hydrolysis of a number of p-nitrophenyl esters of N-alpha-carbobenzoxy-L-amino acids have been also determined between pH 4.0 and 8.0 and compared with those of b.beta-trypsin and b.alpha-chymotrypsin. For all the substrates examined the acylation step (k+2) is rate limiting in the p.p. elastase catalysis, between pH 4.0 and 8.0. The different catalytic behaviours of p.p. elastase, b.beta-trypsin and b.alpha-chymotrypsin are consistent with the known three-dimensional structures of these serine proteases.

Thermodynamic properties of oxygen equilibria of dimeric and tetrameric hemoglobins from Scapharca inaequivalvis

Oxygen equilibrium curves of the dimeric and tetrameric hemoglobin components of Scapharca inaequivalvis were determined at several temperatures. The oxygen equilibrium curves were analyzed by the two-step and four-step oxygen equilibrium schemes of Adair for the dimeric and tetrameric hemoglobins, respectively. The enthalpy and entropy changes for each oxygenation step were determined by the temperature dependences of the Adair constants using van't Hoff equations. Neither dimeric nor tetrameric hemoglobins release protons or anions upon oxygenation under the experimental conditions of the present study. The enthalpy and entropy changes are non-uniform with respect to the oxygenation step and do not need to be corrected for the oxygenation-linked release of protons and anions. For the tetrameric hemoglobin, enthalpy-entropy compensation was observed between the first, second and third steps of oxygenation. The present results suggest that the origin of the co-operative oxygenation is primarily entropic for both hemoglobin components of S. inaequivalvis. Comparison of these data with those obtained on other hemoglobins shows that no simple generalization can be made as to the thermodynamic nature of co-operativity in oxygen binding.

Reactivity of ferrous heme proteins at low pH

The pH rate profile of sperm whale myoglobin (Mb) reacting with CO has been confirmed to follow the behavior previously reported (Giacometti, G.M., Traylor, T.G., Ascenzi, P., Brunori, M., and Antonini, E. (1977) J. Biol. Chem. 252, 7447-7448), and appears to be different from that obtained by others. The pH investigation has been extended to the CO-binding rates of Chironomus thummi thummi erythrocruorin and Aplysia limacina Mb, whose pH rate profile is different from that of sperm whale Mb. Besides the "base dissociation" mechanism previously invoked, the iron atom-heme plane distance is discussed as a possible determinant of the CO reactivity in these monomeric heme proteins.

Kinetic and thermodynamic parameters for oxygen binding to the allosteric states of panulirus interruptus hemocyanin

The temperature dependence of the oxygen binding equilibria and kinetics of Panulirus interruptus hemocyanin has been analyzed within the context of the two-state allosteric model. Oxygenation of the T-state is characterized by a more negative value of DeltaH than that of the R-state; therefore, cooperative effects in oxygen binding to P. interruptus hemocyanin are thermodynamically governed by favorable entropy changes. The allosteric transition in the unliganded derivative shows an enthalpy-entropy compensation effect. The activation enthalpies for oxygenation and deoxygenation of the T-state are larger than those for the R-state, while the activation entropies are favorable for the T-state and unfavorable for the R-state. Thus, the activation free energies for oxygen binding to the T- and R-states are similar, while for the deoxygenation reaction DeltaG++ is smaller for the T-state. The analysis reported confirms the applicability of the Monod-Wyman-Changeux two-state allosteric model to P. interruptus hemocyanin and yields a complete thermodynamic characterization of oxygen binding under both equilibrium and dynamic regimes.

Transient removal of proflavine inhibition of bovine beta-trypsin by the bovine basic pancreatic trypsin inhibitor (Kunitz). A case for "chronosteric effects"

The formation of the bovine beta-trypsin-bovine basic pancreatic trypsin inhibitor (Kunitz) (BPTI) complex was monitored, making use of three different signals: proflavine displacement, optical density changes in the ultraviolet region, and the loss of the catalytic activity. The rates of the reactions indicated by the three different signals were similar at neutral pH, but diverged at low pH. At pH 3.50, proflavine displacement precedes the optical density changes in the ultraviolet and the loss of enzyme activity by several orders of magnitude in time (Antonini, E., Ascenzi, P., Menegatti, E., and Guarneri, M. (1983) Biopolymers 22, 363-375). These data indicated that the bovine beta-trypsin-BPTI complex formation is a multistage process and led to the prediction that, at pH 3.50, BPTI addition to the bovine beta-trypsin-proflavine complex would remove proflavine inhibition and the enzyme would recover transiently its catalytic activity before being irreversibly inhibited by completion of BPTI binding. The kinetic evidences, by completion of BPTI binding. The kinetic evidences, here shown, verified this prediction, indicating that during the bovine beta-trypsin-BPTI complex formation one transient intermediate occurs, which is not able to bind proflavine but may bind and hydrolyze the substrate. Thus, the observed peculiar catalytic behavior is in line with the proposed reaction mechanism for the bovine beta-trypsin-BPTI complex formation, which postulates a sequence of distinct polar and apolar interactions at the contact area.

Binding of terbium to apoferritin: a fluorescence study

Luminescence measurements show that apoferritin binds three Tb(III) atoms per subunit in accordance with crystallographic evidence. Fe(II) competes with Tb(III) for at least some of the binding sites. This competition may be the molecular basis for the inhibition of iron incorporation into apoferritin brought about by Tb(III). Ca(II), which is generally replaced by Tb(III) in Ca(II) binding proteins, does not compete with the lanthanide for binding to apoferritin.

Dimeric and tetrameric hemoglobins from the mollusc Scapharca inaequivalvis. The oxidation reaction

The oxidation by ferricyanide of the dimeric (HbI) and tetrameric (HbII) hemoglobins from the bivalve mollusc Scapharca inaequivalvis has been studied in static and kinetic experiments. Both hemoglobins give rise to hemichromes as stable oxidation products. Oxidation of deoxyHbI yields a hemichrome by a simple bimolecular process. No intermediate Met form can be detected during the reaction even in rapid mixing experiments. The HbI hemichrome undergoes a reversible pH-dependent dissociation into monomers. A simple model has been proposed to account for the linkage between proton binding and subunit dissociation. In the case of tetrameric HbII, oxidation yields an intermediate Met form. Thus, the kinetics of the oxidation reaction are always biphasic; the fast reaction is a bimolecular process and yields the Met derivative. The slow reaction is a monomolecular process and corresponds to the conversion of the Met form into the hemichrome; its rate is independent of the state of ligation of the ferrous protein and decreases with increase of pH. The HbII hemichrome is tetrameric when newly formed; it tends to dissociate into lower molecular weight species with the same optical properties. The rate of dissociation is relatively fast at neutral pH (t 1/2 approximately equal to 12 min) and markedly less at alkaline pH values. The HbI and HbII hemichromes are reduced by dithionite yielding the spectra of the native deoxygenated proteins; in the case of HbII, the tetrameric structure of the native protein is re-acquired.