Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyruvate Synthase”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,513 records · Page 84Linked to original sources
PubMed1992

Adaptation of mitochondrial ATP production in human skeletal muscle to endurance training and detraining.

The adaptation of mitochondrial ATP production rate (MAPR) to training and detraining was evaluated in nine healthy men. Muscle samples (approximately 60 mg) were obtained before and after 6 wk of endurance training and after 3 wk of detraining. MAPR was measured in isolated mitochondria by a bioluminometric method. In addition, the activities of mitochondrial and glycolytic enzymes were determined in skeletal muscle. In response to training, MAPR increased by 70%, with a substrate combination of pyruvate + palmitoyl-L-carnitine + alpha-ketoglutarate + malate, by 50% with only pyruvate + malate, and by 92% with palmitoyl-L-carnitine + malate. With detraining MAPR decreased by 12-28% from the posttraining rate (although not significantly for all substrates). No differences were found when MAPR was related to the protein content in the mitochondrial fraction. The largest increase in mitochondrial enzyme activities induced by training was observed for cytochrome-c oxidase (78%), whereas succinate cytochrome c reductase showed only an 18% increase. The activity of citrate synthase increased by 40% and of glutamate dehydrogenase by 45%. Corresponding changes in maximal O2 uptake were a 9.6% increase by training and a 6.0% reversion after detraining. In conclusion, both MAPR and mitochondrial enzyme activities are shown to increase with endurance training and to decrease with detraining.

Adenosine Triphosphate↗
PubMedDate not supplied

Effect of hypoxia, aging and pharmacological treatment on muscular metabolites and enzyme activities.

The effect of hypoxia and post-hypoxic recovery were studied in gastrocnemius muscle of young-adult and mature beagle dogs. Furthermore, the possible interference of pharmacological treatment with nicergoline was evaluated in these conditions. Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose 6-phosphate, pyruvate, lactate), Kreb's cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate) and related free amino acids (glutamate, alanine), ammonium ion, energy store and mediators (ATP, ADP, AMP and creatine phosphate), and the energy charge potential were evaluated. Furthermore, in the crude extract and/or mitochondrial fraction of another portion of the same gastrocnemius muscle the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway (hexokinase, lactate dehydrogenase), the Kreb's cycle (citrate synthase, malate dehydrogenase), the aminoacid pool related to the Krebs' cycle (glutamate dehydrogenase and aspartate aminotransferase), the electron transfer chain (cytochrome oxidase) and NAD+/NADH exchanges (total NADH cytochrome c reductase) was evaluated. Some glycolytic metabolites and Krebs' cycle intermediates were modified by acute hypoxia, while free amino acids and energy mediators remained practically unchanged. The pharmacological treatment maintained the glucose and succinate muscular concentrations within the normal range, during hypoxia. The behaviour of muscular metabolites during hypoxia and/or post-hypoxic recovery is an age-related event. In fact, only in young-adult animals did the altered values return to normal in post-hypoxic recovery. In the present experimental conditions, only minor changes were observed as far as muscular enzyme activities are concerned. In any case, some enzyme activities tested showed different Vmax in young-adult dogs in comparison with mature ones.

Aging↗
PubMed1994

Purification and characterization of the oxygen-sensitive acetohydroxy acid synthase from the archaebacterium Methanococcus aeolicus.

Acetohydroxy acid synthase (EC 4.1.3.18) of the archaebacterium Methanococcus aeolicus was purified 1,150-fold to homogeneity. The molecular weight of the purified enzyme was 125,000, and it contained only one type of subunit (M(r) = 58,000). The amino-terminal sequence had 46 to 57% similarity to those of the large subunits of the eubacterial anabolic enzymes and 37 to 43% similarity to those of the yeast and plant enzymes. The methanococcal enzyme had a pH optimum of 7.6. The pI, estimated by chromatofocusing, was 5.6. Activity required Mg2+ or Mn2+ ions, thiamine pyrophosphate, and a flavin. Flavin adenine dinucleotide, flavin mononucleotide, and riboflavin plus 10 mM phosphate all supported activity. However, activity was strongly inhibited by these flavins at 0.3 mM. The Michaelis constants for pyruvate, MgCl2, MnCl2, thiamine pyrophosphate, flavin adenine dinucleotide, and flavin mononucleotide were 6.8 mM, 0.3 mM, 0.16 mM, 1.6 microM, 0.4 microM, and 1.3 microM, respectively. In cell extracts, the enzyme was sensitive to O2 (half-life = 2.7 min with 5% O2 in the headspace), but the purified enzyme was less sensitive to O2 (half-life = 78.0 min with 20% O2). Reconstitution of the enzyme with flavin adenine dinucleotide increased the sensitivity to O2. Moreover, in the assay the homogeneous enzyme was rapidly inactivated by O2, and the concentration required for 50% inhibition (I50) was obtained with an atmosphere of 0.11% O2. The methanococcal enzyme has similarities to the eubacterial and eucaryotic enzymes, consistent with the ancient origin of the archaebacterial enzyme.

Acetolactate Synthase↗
PubMed2004

Phototrophic utilization of taurine by the purple nonsulfur bacteria Rhodopseudomonas palustris and Rhodobacter sphaeroides.

Taurine metabolism by two phototrophically grown purple nonsulfur bacteria enrichment isolates has been examined. Rhodopseudomonas palustris (strain Tau1) grows with taurine as a sole electron donor, sulfur and nitrogen source during photoautotrophic growth. Rhodobacter sphaeroides (strain Tau3) grows on the compound as sole electron donor, sulfur and nitrogen source, and partial carbon source, in the presence of CO(2) during photoheterotrophic growth. Both organisms utilize an inducible taurine-pyruvate aminotransferase and a sulfoacetaldehyde acetyltransferase. The products of this metabolism are bisulfite and acetyl phosphate. Bisulfite ultimately was oxidized to sulfate, but this was not an adequate source of electrons for photometabolism. Experiments using either [U-(14)C]taurine or (14)CO(2) demonstrated that Rb. sphaeroides Tau3 assimilated the carbon from approximately equimolar amounts of taurine and exogenous CO(2). The taurine-carbon assimilation was not diminished by excess non-radioactive bicarbonate. Malate synthase (but not isocitrate lyase) was induced in these taurine-grown cells. It is concluded that assimilation of taurine carbon occurs through an intermediate other than CO(2). Similar labelling experiments with Rp. palustris Tau1 determined that taurine is utilized only as an electron donor for the reduction of CO(2), which contributes all the cell carbon. Photoautotrophic metabolism was confirmed in this organism by the absence of either malate synthase or isocitrate lyase in taurine+CO(2)-grown cells. Culture collection strains of these two bacteria did not utilize taurine in these fashions.

Bicarbonates↗
PubMed2006

ACE inhibition prevents myocardial infarction-induced skeletal muscle mitochondrial dysfunction.

Heart failure is associated with alterations in cardiac and skeletal muscle energy metabolism resulting in a generalized myopathy. We investigated the molecular and cellular effects of angiotensin-converting enzyme inhibition (ACEi) on skeletal muscle metabolism in infarcted animals. Myocardial infarction (MI) was obtained by left descending coronary artery ligation. Sham, MI, and MI-treated rats (perindopril, 2 mg.kg(-1).day(-1) given 7 days after MI) were studied 1 and 4 mo after surgery. Oxygen consumption of white gastrocnemius (Gas) muscle was studied in saponin-permeabilized fibers, using the main substrates of mitochondrial respiration. mRNA expression of nuclear factors (PGC-1alpha, NRF-2alpha, and mtTFA), involved in the transcription of mitochondrial proteins, and of MCIP1, a marker of calcineurin activation, were also determined. Echocardiographic left ventricular fractional shortening was reduced in both MI and perindopril group after 1 and 4 mo, whereas systemic blood pressure was reduced by 16% only in the MI group after 4 mo. The capacity of Gas to oxidize glutamate-malate, glycerol-triphosphate, or pyruvate (-30%, P < 0.01; -32%, P < 0.05; -33%, P < 0.01, respectively), was greatly decreased. Furthermore, PGC-1alpha (-54%), NRF-2alpha (-45%), and MCIP1 (-84%) gene expression were significantly downregulated. ACEi improved survival, left ventricular function, and blood pressure. Perindopril protected also totally the Gas mitochondrial function and preserved the mRNAs concentration of the mitochondrial transcriptional factors. Moreover, PGC-1alpha correlated with Gas oxidative capacity (r = 0.48), mitochondrial cytochrome-c oxidase (r = 0.65), citrate synthase (r = 0.45) activities, and MCIP1 expression (r = 0.44). Thus ACEi totally prevented MI-induced alterations of skeletal muscle mitochondrial function and protein expression, halting the development of this metabolic myopathy.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1980

Electron-cytochemical localization of phospho(enol)pyruvate carboxylase (EC 4.1.1.31) in fungal cells.

New cytochemical method, based on biochemical experiments, was elaborated for the ultrastructural localization of phospho(enol)pyruvate carboxylase (EC 4.1.1.31). The procedure was used to study the saprophytic submerged mycelium of the ascomycetous fungus Claviceps purpurea Tul. producing clavine alkaloids. The pelleted mycelium was fixed in ice cold 3% glutaraldehyde in 50 mM cacodylate buffer pH 7.2 and washed repeatedly in the same cold buffer The reaction mixture contained 100 mM Tris-HCl buffer pH 9.0, 10 mM phospho(enol)pyruvate, 30 mM sodium potassium tartrate, 3 mM Pb(NO3)2, 60 mM MgCl2 and 30 mM NaHCO3. Enzyme activity was localized in vacuoles, particularly inside lipid globules (spherosomes) and less frequently in membranous vesicles. Acetyl-CoA activated PEP-carboxylase both in cell free extracts and in the cytochemical staining. Aspartate inhibited the enzyme in the biochemical assay with coupled malate dehydrogenase system; the cytochemical reaction was not influenced, probably due to the interference of asparagine synthase (EC 6.3.1.1).

Carboxy-Lyases↗
PubMedDate not supplied

The evolution of acetyl-CoA synthase.

Acetyl-coenzyme A synthases (ACS) are Ni-Fe-S containing enzymes found in archaea and bacteria. They are divisible into 4 classes. Class I ACS's catalyze the synthesis of acetyl-CoA from CO2 + 2e-, CoA, and a methyl group, and contain 5 types of subunits (alpha, beta, gamma, delta, and epsilon). Class II enzymes catalyze essentially the reverse reaction and have similar subunit composition. Class III ACS's catalyze the same reaction as Class I enzymes, but use pyruvate as a source of CO2 and 2e-, and are composed of 2 autonomous proteins, an alpha 2 beta 2 tetramer and a gamma delta heterodimer. Class IV enzymes catabolize CO to CO2 and are alpha-subunit monomers. Phylogenetic analyses were performed on all five subunits. ACS alpha sequences divided into 2 major groups, including Class I/II sequences and Class III/IV-like sequences. Conserved residues that may function as ligands to the B- and C-clusters were identified. Other residues exclusively conserved in Class I/II sequences may be ligands to additional metal centers in Class I and II enzymes. ACS beta sequences also separated into two groups, but they were less divergent than the alpha's, and the separation was not as distinct. Class III-like beta sequences contained approximately 300 residues at their N-termini absent in Class I/II sequences. Conserved residues identified in beta sequences may function as ligands to active site residues used for acetyl-CoA synthesis. ACS gamma-sequences separated into 3 groups (Classes I, II, and III), while delta-sequences separated into 2 groups (Class I/II and III). These groups are less divergent than those of alpha sequences. ACS epsilon-sequence topology showed greater divergence and less consistency vis-à-vis the other subunits, possibly reflecting reduced evolutionary constraints due to the absence of metal centers. The alpha subunit phylogeny may best reflect the functional diversity of ACS enzymes. Scenarios of how ACS and ACS-containing organisms may have evolved are discussed.

Acetate-CoA Ligase↗
PubMed2006

Crystal structure of 1-deoxy-D-xylulose 5-phosphate synthase, a crucial enzyme for isoprenoids biosynthesis.

Isopentenyl pyrophosphate (IPP) is a common precursor for the synthesis of all isoprenoids, which have important functions in living organisms. IPP is produced by the mevalonate pathway in archaea, fungi, and animals. In contrast, IPP is synthesized by a mevalonate-independent pathway in most bacteria, algae, and plant plastids. 1-Deoxy-D-xylulose 5-phosphate synthase (DXS) catalyzes the first and the rate-limiting step of the mevalonate-independent pathway and is an attractive target for the development of novel antibiotics, antimalarials, and herbicides. We report here the first structural information on DXS, from Escherichia coli and Deinococcus radiodurans, in complex with the coenzyme thiamine pyrophosphate (TPP). The structure contains three domains (I, II, and III), each of which bears homology to the equivalent domains in transketolase and the E1 subunit of pyruvate dehydrogenase. However, DXS has a novel arrangement of these domains as compared with the other enzymes, such that the active site of DXS is located at the interface of domains I and II in the same monomer, whereas that of transketolase is located at the interface of the dimer. The coenzyme TPP is mostly buried in the complex, but the C-2 atom of its thiazolium ring is exposed to a pocket that is the substrate-binding site. The structures identify residues that may have important roles in catalysis, which have been confirmed by our mutagenesis studies.

Amino Acid Sequence↗
PubMed1995

Microbial production of specifically ring-13C-labelled 4-hydroxybenzoic acid.

When transformed with a recombinant vector carrying the ubiC gene (encoding chorismate pyruvate-lyase, EC 4.1.3.27) the triple mutant (Phe-, Trp-, Tyr-) Klebsiella pneumoniae 62-1 excretes 4-hydroxybenzoic acid instead of chorismic acid. The recombinant strain can be used to produce in high yield specifically ring-labelled 4-hydroxybenzoic acid from isotopically labelled glucose.

Anthranilate Synthase↗
PubMed1977

Localisation and characterization of the fatty acid synthesizing system in cells of Glycine max (soubean) suspension cultures.

In course of a study of fatty acid synthetase in higher plants, non-green cell suspension cultures of Glycine max (soybean) served as model tissues. For the first time, a fatty acid synthesizing system was characterized in cell cultures of higher plants and was found to be solely located in proplastids of the cells. Optimum activity of the fatty acid synthesizing system in proplastids was observed between pH 8.0 and 8.2; with [1-14C]acetate as substrate, cofactors required were CoA, ATP, Mn2+, Mg2+, HCO3-, NADH and NADPH. The system was more sensitive towards NADH than NADHP. [1-14C]Acetate,[2-14C]-malonate and [3-14C]pyruvate served as precursors for fatty acids, indicating the presence of pyruvate dehydrogenase activity in proplastids. In disrupted proplastids, [2-14C]malonylCoA was a better precursor than [1-14C]acetylCoA. After incubation of proplastids with [2-14C]malonate, a small shift, from palmitic acid to higher homologs, of label incorporated was observed, as compared to incorporation of label from [1-14C]acetate and [3-14C]pyruvate. Under the conditions of the experiment, only small amounts of polyunsaturated fatty acids, the main fatty acid components of this organelle, were synthesized. In respect to fatty acid synthesis, the non-green cell suspension culture resembles photosynthetic leaf tissue.

Cells, Cultured↗
PubMed2003

The monocarboxylate transport inhibitor, alpha-cyano-4-hydroxycinnamate, has no effect on retinal ischemia.

Glial-derived monocarboxylate lactate is thought to be an important energy source for neurons during brain activation or in hypoxia-ischemia. Treatment with alpha-cyano-4-hydroxycinnamate (4-CIN), a monocarboxylate transporter inhibitor, has been recently reported to exacerbate delayed neuronal damage in a rat model of cerebral ischemia, an effect ascribed to inhibition of lactate/pyruvate transport. Since monocarboxylate transporters are abundant in the retina, we examined the effect of 4-CIN administration on the outcome of high intraocular pressure-induced retinal ischemia in rats. Retinal ischemic damage was assessed by changes in the electroretinogram (ERG), the retinal localization of choline acetyltransferase (ChAT) and neuronal nitric oxide synthase (nNOS) immunoreactivities, and the loss of retinal mRNA for Thy-1. Intraperitoneal or intravitreal administration of 4-CIN had no effect on the ERG or the localization of ChAT and nNOS immunoreactivities in either the control retina or a retina subjected to ischemia/reperfusion. In addition, intravitreal injection of 4-CIN had no effect on ischemia-induced reduction of retinal mRNA levels for Thy-1. These results provide no evidence to support the view that blockade of lactate uptake and/or pyruvate entry into mitochondria for oxidative metabolism has an influence on the outcome of retinal ischemia/reperfusion.

Animals↗
PubMed1996

Insulin- and polyunsaturated fatty acid-responsive region(s) of rat ATP citrate lyase gene promoter.

To investigate the regulatory DNA sequences required for insulin-stimulation of the ATP citrate-lyase (ACL) gene as well as for polyunsaturated fatty acid (PUFA)-suppression of this gene, primary cultured hepatocytes were transfected with plasmids containing the 5'-flanking sequence of the rat ACL gene fused to the chloramphenicol acetyltransferase (CAT) gene. Sequences from -861, -194 or -104 to +128 of the ACl gene directed an increase in CAT activity in hepatocytes when insulin was added to the medium containing either glucose or pyruvate. The CAT activities stimulated by insulin were reduced by the addition of PUFA, in accordance with the responses on the endogenous ACL gene expression. Further deletion to -20, however, resulted in loss of the responses. The results suggest that the region from -104 to -20 of the ACL gene is responsible for regulation due to insulin and PUFAs. In particular, the region from -61 to -49 of the ACL has sequence similarity to the insulin-responsive regions of fatty acid synthase and acetyl-CoA carboxylase.

ATP Citrate (pro-S)-Lyase↗
PubMed1997

Regulation of the expression of lipogenic enzyme genes by carbohydrate.

Diets high in simple carbohydrates and low in fats lead in the mammalian liver to induction of a set of enzymes involved in lipogenesis. This induction occurs, in part, through transcriptional mechanisms that lead to elevated levels of the mRNA for these enzymes. For most of the lipogenic enzymes, an increase in glucose metabolism is required to trigger the transcriptional response. The intracellular mediator of this signaling pathway is unknown, although evidence suggests either glucose-6-phosphate or xylulose-5-phosphate. Studies to map the regulatory sequences of lipogenic enzyme genes involved in the transcriptional response have been performed for the L-type pyruvate kinase, S14, and acetyl-coenzyme A carboxylase genes. These studies have identified the DNA sequences necessary to link the signal generated by carbohydrate metabolism to specific nuclear transcription factors.

ATP Citrate (pro-S)-Lyase↗
PubMed1994

Coupling of muscle phosphorylation potential to glycolysis during work after short-term training.

To examine whether the metabolic adaptations to short-term training are expressed over a range of submaximal levels of mitochondrial respiration, seven untrained male subjects [maximal O2 uptake (VO2max) = 45.9 +/- 1.9 (SE) ml.kg-1.min-1] performed a progressive three-stage protocol of cycle exercise at 60% (20 min), 79% (20 min), and 92% (11 min) of pretraining VO2max before and after training. Training consisted of 5-6 days of cycling for 2 h/day at 65% VO2max. Muscle tissue rapidly obtained from the vastus lateralis by needle biopsy indicated that training blunted (P < 0.05) the increase in lactate observed at 60% (23.4 +/- 6.5 vs. 12.4 +/- 2.9 mmol/kg dry wt), 79% (48.9 +/- 5.1 vs. 25.6 +/- 5.2 mmol/kg dry wt), and 92% (68.3 +/- 6.4 vs. 41.5 +/- 6.5 mmol/kg dry wt) of VO2max. Training also resulted in a higher phosphocreatine and lower creatine and P(i) concentrations at both 79% (P < 0.05) and 92% (P < 0.05) of VO2max and higher muscle glycogen levels (P < 0.05). These changes were accompanied by small but significant reductions (P < 0.05) in O2 uptake at the two higher exercise intensities. Given that the lactate-to-pyruvate ratio and the calculated free ADP and AMP were also reduced (P < 0.05), it would appear that short-term training results in a tighter metabolic control over a range of mitochondrial respiratory rates.

Adult↗
PubMed1985

Multiple requirements for glycogen synthesis by hepatocytes isolated from fasted rats.

Glycogen synthesis from various combinations of substrates by hepatocytes isolated from rats fasted 24 h was studied. As reported by Katz et al. (Katz, J., Golden, S., and Wals, P. A. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 3433-3437), appreciable rates of glycogen synthesis occurred only in the presence of gluconeogenic precursors and one of several amino acids, which includes L-glutamine. L-Leucine had negligible effects on glycogen synthesis from 20 mM dihydroxyacetone and/or 15 mM glucose when L-glutamine was not added to the medium. In the presence of 10 mM L-glutamine, L-leucine greatly increased glycogen synthesis from these substrates. alpha-Ketoisocaproate was ineffective, as was oleate. NH4Cl depressed glycogen synthesis from 10 mM glucose plus 20 mM dihydroxyacetone in the absence of added L-glutamine and enhanced that in its presence, but these effects were weak compared to those of L-leucine. The amino acid analogues L-norvaline and L-norleucine exerted effects that were similar to those exerted by L-leucine. Under all conditions studied, cycloheximide and puromycin inhibited net glycogen synthesis. Cycloheximide did not stimulate gluconeogenesis from dihydroxyacetone, or phosphorylase in hepatocytes from starved rats, or glycogenolysis in hepatocytes from fed rats. Puromycin, however, stimulated glycogenolysis in hepatocytes from fed rats. Glycogen synthesis from 20 mM dihydroxyacetone proceeds with a pronounced initial lag phase that can be shortened by incubation of cells with glutamine plus leucine before addition of dihydroxyacetone. Concurrent measurements of glycogen synthesis, glycogen synthase, and gluconeogenesis under different conditions reveal that in addition to protein synthesis, activation of glycogen synthase, which must occur to allow glycogen synthesis in hepatocytes, requires a second component which can be satisfied by addition of dihydroxyacetone or fructose to the cells.

Amino Acids, Branched-Chain↗
PubMed2005

Two consecutive aspartic acid residues conferring herbicide resistance in tobacco acetohydroxy acid synthase.

Acetohydroxy acid synthase (AHAS) catalyzes the first common step in the biosynthesis pathway of the branch chain amino acids in plants and microorganisms. A great deal of interest has been focused on AHAS since it was identified as the target of several classes of potent herbicides. In an effort to produce a mutant usable in the development of an herbicide-resistant transgenic plant, two consecutive aspartic acid residues, which are very likely positioned next to the enzyme-bound herbicide sulfonylurea as the homologous residues in AHAS from yeast, were selected for this study. Four single-point mutants and two double mutants were constructed, and designated D374A, D374E, D375A, D375E, D374A/D375A, and D374E/D375E. All mutants were active, but the D374A mutant exhibited substrate inhibition at high concentrations. The D374E mutant also evidenced a profound reduction with regard to catalytic efficiency. The mutation of D375A increased the K(m) value for pyruvate nearly 10-fold. In contrast, the D375E mutant reduced this value by more than 3-fold. The double mutants exhibited synergistic reduction in catalytic efficiencies. All mutants constructed in this study proved to be strongly resistant to the herbicide sulfonylurea Londax. The double mutants and the mutants with the D375 residue were also strongly cross-resistant to the herbicide triazolopyrimidine TP. However, only the D374A mutant proved to be strongly resistant to imidazolinone Cadre. The data presented here indicate that the two residues, D374 and D375, are located at a common binding site for the herbicides sulfonylurea and triazolopyrimidine. D375E may be a valuable mutant for the development of herbicide-resistant transgenic plants.

Acetolactate Synthase↗
PubMed2004

MosA, a protein implicated in rhizopine biosynthesis in Sinorhizobium meliloti L5-30, is a dihydrodipicolinate synthase.

MosA is a gene product encoded on a pSym megaplasmid of Sinorhizobium meliloti L5-30. The gene is part of an operon reported to be essential for the synthesis of the rhizopine 3-O-methyl-scyllo-inosamine. MosA has been assigned the function of an O-methyltransferase. However, the reported sequence of this protein is very much like that of dihydrodipicolinate synthase (DHDPS), except for a 40 amino acid residue C-terminal domain. This similarity contradicts accepted ideas regarding structure-function relationships of enzymes. We have cloned and overexpressed the recombinant gene in Escherichia coli, and discovered that the reported sequence contains an error resulting in a frame-shift. The correct sequence contains a new stop codon, truncating the C-terminal 41 amino acid residues of the reported sequence. The expressed protein, bearing an N-terminal polyhistidine tag, catalyzes the condensation of pyruvate and aspartate beta-semialdehyde efficiently, suggesting that this activity is not a side-reaction, but an activity for which this enzyme has evolved. Electro-spray mass spectrometry experiments and inhibition by L-lysine are consistent with the enzyme being a DHDPS. E.coli AT997, a mutant host normally requiring exogenous diaminopimelate for growth, could be complemented by transformation with a plasmid bearing the gene encoding MosA. A role for this enzyme in rhizopine synthesis cannot be ruled out, but is called into question.

Amino Acid Sequence↗
PubMed1994

Effects of glucose on sorbitol pathway activation, cellular redox, and metabolism of myo-inositol, phosphoinositide, and diacylglycerol in cultured human retinal pigment epithelial cells.

Sorbitol (aldose reductase) pathway flux in diabetes perturbs intracellular metabolism by two putative mechanisms: reciprocal osmoregulatory depletion of other organic osmolytes e.g., myo-inositol, and alterations in NADPH/NADP+ and/or NADH/NAD+. The "osmolyte" and "redox" hypotheses predict secondary elevations in CDP-diglyceride, the rate-limiting precursor for phosphatidylinositol synthesis, but through different mechanisms: the "osmolyte" hypothesis via depletion of intracellular myo-inositol (the cosubstrate for phosphatidylinositol-synthase) and the "redox" hypothesis through enhanced de novo synthesis from triose phosphates. The osmolyte hypothesis predicts diminished phosphoinositide-derived arachidonyl-diacylglycerol, while the redox hypothesis predicts increased total diacylglycerol and phosphatidic acid. In high aldose reductase expressing retinal pigment epithelial cells, glucose-induced, aldose reductase inhibitor-sensitive CDP-diglyceride accumulation and inhibition of 32P-incorporation into phosphatidylinositol paralleled myo-inositol depletion (but not cytoplasmic redox, that was unaffected by glucose) and depletion of arachidonyl-diacylglycerol. 3 mM pyruvate added to the culture medium left cellular redox unaltered, but stimulated Na(+)-dependent myo-inositol uptake, accumulation, and incorporation into phosphatidylinositol. These results favor myo-inositol depletion rather than altered redox as the primary cause of glucose-induced aldose reductase-related defects in phospholipid metabolism in cultured retinal pigment epithelial cells.

Aldehyde Reductase↗