Mammalian methylmalonate-semialdehyde dehydrogenase

Lipid and protein corona of food-grade TiO2 nanoparticles in simulated gastrointestinal digestion

In the presence of biological matrices, engineered nanomaterials, such as TiO₂, develop a biomolecular corona composed of lipids, proteins, etc. In this study, we analyzed the biocorona formed on the food grade TiO₂ (E171) going through an in vitro simulated gastrointestinal digestion system in either a fasting food model (FFM), a standardized food model (SFM), or a high fat food model (HFFM). Lipids and proteins were extracted from the biocorona and underwent untargeted lipidomic and label-free shotgun proteomic analyses. Our results showed that the biocorona composition was different before and after food digestion. After digestion, more diverse lipids were adsorbed compared to proteins, most of which were the enzymes added to the simulated digestion system. The corona lipid profile was distinct from the digested food model they presented in, although similarity in the lipid profiles between the corona and the food matrix increased with the fat content in the food model. The corona formed in the two low-fat environments of FFM and SFM shared a higher degree of similarity while very different from their corresponding matrix, with some lipid species adsorbed with high enrichment factors, indicating specific interaction with the TiO₂ surface outperforming lipid matrix concentration in determination of corona formation. Formation of the biocorona may have contributed to the reduced oxidative stress as well as toxicological impacts observed in cellular studies. The present work is the first to confirm persistent adsorption of biomolecules could occur on ingested nanomaterials in food digestae. More future studies are needed to study the in vivo impacts of the biocorona, and shed lights on how the biocorona affects the biotransformations and fate of the ingested nanomaterials, which may impose impacts on human health.

The Unusual Suspects in Cytokinesis: Fitting the Pieces Together

Cytokinesis is the step of the cell cycle in which the cell must faithfully separate the chromosomes and cytoplasm, yielding two daughter cells. The assembly and contraction of the contractile network is spatially and temporally coupled with the formation of the mitotic spindle to ensure the successful completion of cytokinesis. While decades of studies have elucidated the components of this machinery, the so-called usual suspects, and their functions, many lines of evidence are pointing to other unexpected proteins and sub-cellular systems as also being involved in cytokinesis. These we term the unusual suspects. In this review, we introduce recent discoveries on some of these new unusual suspects and begin to consider how these subcellular systems snap together to help complete the puzzle of cytokinesis.

Inter-relations between 3-hydroxypropionate and propionate metabolism in rat liver: relevance to disorders of propionyl-CoA metabolism

Propionate, 3-hydroxypropionate (3HP), methylcitrate, related compounds, and ammonium accumulate in body fluids of patients with disorders of propionyl-CoA metabolism, such as propionic acidemia. Although liver transplantation alleviates hyperammonemia, high concentrations of propionate, 3HP, and methylcitrate persist in body fluids. We hypothesized that conserved metabolic perturbations occurring in transplanted patients result from the simultaneous presence of propionate and 3HP in body fluids. We investigated the inter-relations of propionate and 3HP metabolism in perfused livers from normal rats using metabolomic and stable isotopic technologies. In the presence of propionate, 3HP, or both, we observed the following metabolic perturbations. First, the citric acid cycle (CAC) is overloaded but does not provide sufficient reducing equivalents to the respiratory chain to maintain the homeostasis of adenine nucleotides. Second, there is major CoA trapping in the propionyl-CoA pathway and a tripling of liver total CoA within 1 h. Third, liver proteolysis is stimulated. Fourth, propionate inhibits the conversion of 3HP to acetyl-CoA and its oxidation in the CAC. Fifth, some propionate and some 3HP are converted to nephrotoxic maleate by different processes. Our data have implications for the clinical management of propionic acidemia. They also emphasize the perturbations of the liver intermediary metabolism induced by supraphysiological, i.e., millimolar, concentrations of labeled propionate used to trace the intermediary metabolism, in particular, inhibition of CAC flux and major decreases in the [ATP]/[ADP] and [ATP]/[AMP] ratios.

Methylmalonate-semialdehyde dehydrogenase mediated metabolite homeostasis essentially regulate conidiation, polarized germination and pathogenesis in Magnaporthe oryzae

Plants generate multitude of aldehydes under abiotic and biotic stress conditions. Ample demonstrations have shown that rice-derived aldehydes enhance the resistance of rice against the rice-blast fungus Magnaporthe oryzae. However, how the fungal pathogen nullifies the inhibitory effects of host aldehydes to establish compatible interaction remains unknown. Here we identified and evaluated the in vivo transcriptional activities of M. oryzae aldehyde dehydrogenase (ALDH) genes. Transcriptional analysis of M. oryzae ALDH genes revealed that the acetylating enzyme Methylmalonate-Semialdehyde Dehydrogenase (MoMsdh/MoMmsdh) elevated activities during host invasion and colonization of the fungus. We further examined the pathophysiological importance of MoMSDH by deploying integrated functional genetics, and biochemical approaches. MoMSDH deletion mutant ΔMomsdh exhibited germination defect, hyper-branching of germ tube and failed to form appressoria on hydrophobic and hydrophilic surface. The MoMSDH disruption caused accumulation of small branch-chain amino acids, pyridoxine and AMP/cAMP in the ΔMomsdh mutant and altered Spitzenkörper organization in the conidia. We concluded that MoMSDH contribute significantly to the pathogenesis of M. oryzae by regulating the mobilization of Spitzenkörper during germ tube morphogenesis, appressoria formation by acting as metabolic switch regulating small branch-chain amino acids, inositol, pyridoxine and AMP/cAMP homeostasis.

Severe child form of primary hyperoxaluria type 2 - a case report revealing consequence of GRHPR deficiency on metabolism

BACKGROUND

Primary hyperoxaluria type 2 is a rare monogenic disorder inherited in an autosomal recessive pattern. It results from the absence of the enzyme glyoxylate reductase/hydroxypyruvate reductase (GRHPR). As a consequence of deficient enzyme activity, excessive amounts of oxalate and L-glycerate are excreted in the urine, and are a source for the formation of calcium oxalate stones that result in recurrent nephrolithiasis and less frequently nephrocalcinosis.

CASE PRESENTATION

We report a case of a 10-month-old patient diagnosed with urolithiasis. Screening of inborn errors of metabolism, including the performance of GC/MS urine organic acid profiling and HPLC amino acid profiling, showed abnormalities, which suggested deficiency of GRHPR enzyme. Additional metabolic disturbances observed in the patient led us to seek other genetic determinants and the elucidation of these findings. Besides the elevated excretion of 3-OH-butyrate, adipic acid, which are typical marks of ketosis, other metabolites such as 3-aminoisobutyric acid, 3-hydroxyisobutyric acid, 3-hydroxypropionic acid and 2-ethyl-3-hydroxypropionic acids were observed in increased amounts in the urine. Direct sequencing of the GRHPR gene revealed novel mutation, described for the first time in this article c.454dup (p.Thr152Asnfs*39) in homozygous form. The frequent nucleotide variants were found in AGXT2 gene.

CONCLUSIONS

The study presents metabolomic and molecular-genetic findings in a patient with PH2. Mutation analysis broadens the allelic spectrum of the GRHPR gene to include a novel c.454dup mutation that causes the truncation of the GRHPR protein and loss of its two functional domains. We also evaluated whether nucleotide variants in the AGXT2 gene could influence the biochemical profile in PH2 and the overproduction of metabolites, especially in ketosis. We suppose that some metabolomic changes might be explained by the inhibition of the MMSADH enzyme by metabolites that increase as a consequence of GRHPR and AGXT2 enzyme deficiency. Several facts support an assumption that catabolic conditions in our patient could worsen the degree of hyperoxaluria and glyceric aciduria as a consequence of the elevated production of free amino acids and their intermediary products.

The protein expression profile in hepatopancreas of scallop Chlamys farreri under heat stress and Vibrio anguillarum challenge

Heat stress and pathogen infection have been considered as the main causes for mass mortality of cultured scallops during summer. In the present study, the expression profiles of proteins in the hepatopancreas of scallop Chlamys farreri were examined to reveal the possible mechanisms of physiological responses of scallop beneath heat stress and bacterial infection. An earlier occurred and higher mortality was observed in the scallops from combination treated group (28 °C and an injection of Vibrio anguillarum) in comparison to those in heat stress (28 °C) and bacteria challenge (V. anguillarum injection only) group, as well as control (PBS) and blank (untreated) group. The proteins in the hepatopancreas from scallops post 6 h of treatment were analyzed by using 2-D PAGE and ImageMaster 2D Platinum. There were total 1003 spots detected in control group, 1193 spots in heat stress group, 1263 spots in bacteria challenge group, and 1241 spots in the combination group. Fifteen protein spots expressed differentially between the combination treatment group and the bacteria challenge group were successfully identified by mass spectrometry and they were mainly classified as binding and catalytic proteins, such as endoglucanase, methylmalonate-semialdehyde dehydrogenase, xylose isomerase, tryptophanyl-tRNA synthetase, 40s ribosomal protein SA, glutathione S-transferase 4, and Mitochondrial transcription factor A, etc. These results indicated that the mortality of scallops suffered from the combination treatment was probably attributed to the impaired modulation of digestion and metabolism and ruined protein synthesis caused by heat stress together with bacteria infection. These data also provided valuable insights into the possible mechanisms of summer mortality occurrence of scallop at protein level.

Unraveling the function of paralogs of the aldehyde dehydrogenase super family from Sulfolobus solfataricus

Aldehyde dehydrogenases (ALDHs) have been well established in all three domains of life and were shown to play essential roles, e.g., in intermediary metabolism and detoxification. In the genome of Sulfolobus solfataricus, five paralogs of the aldehyde dehydrogenases superfamily were identified, however, so far only the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) and α-ketoglutaric semialdehyde dehydrogenase (α-KGSADH) have been characterized. Detailed biochemical analyses of the remaining three ALDHs revealed the presence of two succinic semialdehyde dehydrogenase (SSADH) isoenzymes catalyzing the NAD(P)(+)-dependent oxidation of succinic semialdehyde. Whereas SSO1629 (SSADH-I) is specific for NAD(+), SSO1842 (SSADH-II) exhibits dual cosubstrate specificity (NAD(P)(+)). Physiological significant activity for both SSO-SSADHs was only detected with succinic semialdehyde and α-ketoglutarate semialdehyde. Bioinformatic reconstructions suggest a major function of both enzymes in γ-aminobutyrate, polyamine as well as nitrogen metabolism and they might additionally also function in pentose metabolism. Phylogenetic studies indicated a close relationship of SSO-SSALDHs to GAPNs and also a convergent evolution with the SSADHs from E. coli. Furthermore, for SSO1218, methylmalonate semialdehyde dehydrogenase (MSDH) activity was demonstrated. The enzyme catalyzes the NAD(+)- and CoA-dependent oxidation of methylmalonate semialdehyde, malonate semialdehyde as well as propionaldehyde (PA). For MSDH, a major function in the degradation of branched chain amino acids is proposed which is supported by the high sequence homology with characterized MSDHs from bacteria. This is the first report of MSDH as well as SSADH isoenzymes in Archaea.

A comparative proteomic study of nephrogenesis in intrauterine growth restriction

Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction (IUGR), leading to a low nephron endowment. The aim of this study was to test the hypothesis that IUGR affects expression of key proteins that regulate nephrogenesis, by a comparative proteomic approach. IUGR was induced in Sprague-Dawley (SD) rats by isocaloric protein restriction in pregnant dams. A series of methods, including two-dimensional gel electrophoresis (2-DE), silver staining, mass spectrometry and database searching was used. After silver staining, 2-DE image analysis detected an average 730 + or - 58 spots in the IUGR group and 711 + or - 73 spots in the control group. The average matched rate was 86% and 81%, respectively. The differential proteomic expression analysis found that 11 protein spots were expressed only in the IUGR group and one in the control group. Seven protein spots were up-regulated more than fivefold and two were down-regulated more than fivefold in the IUGR group compared with those in control group. These 21 protein spots were preliminarily identified and were structural molecules, including vimentin, perlecan, gamma-actin and cytokeratin 10, transcription regulators, transporter proteins, enzymes, and so on. These proteins were involved primarily in energy metabolism, oxidation and reduction, signal transduction, cell proliferation and apoptosis. Data from this study may provide, at least partly, evidence that abnormality of metabolism, imbalance of redox and apoptosis, and disorder of cellular signal and cell proliferation may be the major mechanisms responsible for abnormal nephrogenesis in IUGR.

Tissue distribution, ontogeny, and regulation of aldehyde dehydrogenase (Aldh) enzymes mRNA by prototypical microsomal enzyme inducers in mice

Aldehyde dehydrogenases (Aldhs) are a group of nicotinamide adenine dinucleotide phosphate-dependent enzymes that catalyze the oxidation of a wide spectrum of aldehydes to carboxylic acids. Tissue distribution and developmental changes in the expression of the messenger RNA (mRNA) of 15 Aldh enzymes were quantified in male and female mice tissues using the branched DNA signal amplification assay. Furthermore, the regulation of the mRNA expression of Aldhs by 15 typical microsomal enzyme inducers (MEIs) was studied. Aldh1a1 mRNA expression was highest in ovary; 1a2 in testis; 1a3 in placenta; 1a7 in lung; 1b1 in small intestine; 2 in liver; 3a1 in stomach; 3a2 and 3b1 expression was ubiquitous; 4a1, 6a1, 7a1, and 8a1 in liver and kidney; 9a1 in liver, kidney, and small intestine; and 18a1 in ovary and small intestine. mRNAs of different Aldh enzymes were detected at lower levels in fetuses than adult mice and gradually increased after birth to reach adult levels between 15 and 45 days of age, when the gender difference began to appear. Aromatic hydrocarbon receptor (AhR) ligands induced the liver mRNA expression of Aldh1a7, 1b1, and 3a1, constitutive androstane receptor (CAR) activators induced Aldh1a1 and 1a7, whereas pregnane X receptor (PXR) ligands and NF-E2 related factor 2 (Nrf2) activators induced Aldh1a1, 1a7, and 1b1. Peroxisome proliferator activator receptor alpha (PPAR alpha) ligands induced the mRNA expression in liver of almost all Aldhs. The Aldh organ-specific distribution may be important in elucidating their role in metabolism, elimination, and organ-specific toxicity of xenobiotics. Finally, in contrast to other phase-I metabolic enzymes such as CYP450 enzymes, Aldh mRNA expression seems to be generally insensitive to typical microsomal inducers except PPAR alpha ligands.