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At least 793 records · Page 44Linked to original sources
PubMedDate not supplied

[Possible pathways for acetyl-CoA formation by purple bacteria].

Purple sulfur (Ectothiorhodospira shaposhnikovii, Chromatium minutissimum, Lamprobacter modestohalophilus, Thiocapsa roseopersicina) and nonsulfur (Rhodospirillum rubrum, Rhodopseudomonas palustris, Rhodopseudomonas spheroides) bacteria are capable of forming acetyl-CoA synthetase, phosphotransacetylase and acetokinase independent of the medium composition and growth conditions. In all of the purple sulfur bacteria with an exception of E. shaposhnikovii, the activity of acetokinase is much higher than in purple nonsulfur bacteria. Apart from being involved in the synthesis of acetyl-CoA, such enzymes as phosphotransacetylase, acetokinase and adenylate kinase may play an important role in energy processes of some purple bacteria in the dark.

Acetyl Coenzyme A↗
PubMed1985

Heterogeneity of holocarboxylase synthetase in patients with biotin-responsive multiple carboxylase deficiency.

Holocarboxylase synthetase activity has been determined in fibroblasts of seven patients with the neonatal form of biotin-responsive multiple carboxylase deficiency. The normal Km for biotin was 15 +/- 3 nmol/l, while in the patients the values ranged from 48 to 1,062 nmol/l. The mean maximum velocity was 27% of normal. Differences among the values obtained for the Km for biotin and the heat stability of holocarboxylase synthetase suggested that the patients studied represented at least four distinct variants at the holocarboxylase synthetase locus.

Biotin↗
PubMed1980

[Relationship between catalytic properties, fixed charge concentration and electrostatic potential of polyelectrolyte-bound enzymes].

An equation for the calculation of the electrostatic potentials of polyelectrolyte-enzyme supports from electrostatic parameters has been derived by relating two different theories which describe the catalytic behaviour of polyelectrolyte-bound enzymes. The electrostatic potentials of polyionic supports have been determined by use of experimental results, on the one hand, from the fixed charge concentration and the ionic strength, on the other hand, from pH- and Km-shifts of immobilized enzymes. The accordance of potentials calculated from electrostatic and kinetic parameters confirms the macroscopic carrier-enzyme model.

Amylases↗
PubMed1983

[Measurement of human seminal components and its medicolegal application].

Microdeterminations for low molecular compounds highly contained in human seminal plasma, i. e., dehydroepiandrosterone sulfate (DHEA-S), spermine (Sp) and citric acid (CA) have been established. Experimental studies were carried out on application of these methods to identification of semen from cadaveric vaginae more than a few days after death. DHEA-S was measured by radioimmunoassay using anti-DHEA-S-17-hydrazone conjugated bovine serum albumin rabbit antiserum. Sp and CA were determined spectrophotometrically with monoamine oxidase and with citrate lyase, oxalacetate decarboxylase and pyruvate oxidase, respectively. DHEA-S and its cross-reacting materials were contained little in saliva, moderately in semen and vaginal contents and largely in serum and urine. By the above method Sp was not detectable in other body fluids except semen. CA was contained not only largely in semen but also a little in other body fluids. DHEA-S and Sp in the seminal fluid allowed to stand at room temperature were relatively stable during a month, whereas CA became undetectable in 10 days, all of which being persistent in seminal stain during at least one month. From these results the colorimetry of Sp among the three methods above mentioned was found to be most reliable for detecting seminal fluid from vaginal contents of a putrefied cadaver.

Body Fluids↗
PubMedDate not supplied

[Effect of elevated hydrostatic pressure on the activity of catabolic enzymes in barotolerant bacteria].

The effect of elevated hydrostatic pressure on catabolic enzymes was studied with four strains of barotolerant bacteria isolated from ooze at high depth of the Pacific Ocean. Pseudomonas aeruginosa 0798 and Ps. sociovivum 0913, tolerant to a pressure of 500 atm, have more active catabolic enzymes than Ps. nonliquefaciens 0613 and Ps. acuta 039, which do not grow at a pressure of 500 atm. Changes in the activity of the enzymes caused by elevated hydrostatic pressure are similar to changes caused by the process of the culture aging.

Bacteria↗
PubMed1976

A respiration-deficient Chinese hamster cell line with a defect in NADH-coenzyme Q reductase.

We have recently described a Chinese hamster cell line with a greatly reduced rate of respiration. In this report we conclude that the defects is in NADH-coenzyme Q reductase (NADH oxidase), the first part of the electron transport chain. The conclusion is based on the following observations. (a) In this and in the earlier report we determined that the relevant enzymes of the Krebs cycle are present and active. (b) Oxygen consumption by isolated mitochondria is normal when driven by succinate and alpha-glycerolphosphate. (c) Difference spectra between reduced and oxidized forms indicate that all cytochromes are present and functional. (d) In contrast, substrates such as malate, glutamate, alpha-ketoglutarate, and isocitrate which generate NADH do not stimulate oxygen consumption in mutant mitochondria. (e) A direct assay of the rotenone-sensitive NADH oxidase in Lubrol-treated mitochondria from mutant cells revealed less than one-tenth of the activity when compared with wild type mitochondria. (f) The treatment of wild type cells with rotenone, a specific inhibitor of NADH-CoQ reductase, yielded an exact phenocopy of the mutant by several criteria. This is the first report of a respiration-deficient mammalian cell mutant in tissue culture.

Cell Line↗
PubMed1976

[Myocardial changes in rats after considerable physical exertion and the effect of pyridoxilate on the severity of these changes].

Under significant physical exercises the myocardium of rats displays distinct enzymopathy, increased permeability of the cell membranes with a considerable dispersion of plasma proteins and damage to the ultrastructures of the myocytes. The employment of pyridoxilate reduces the severity of the damaging reaction, and to some extent normalizes the structure of the cellular and sub-cellular elements of the myocardium. This indicates to the prospects of using the regulators of cellular respiration under total and tissue hypoxia.

Animals↗
PubMed1988

In vivo studies of cysteine metabolism. Use of D-cysteinesulfinate, a novel cysteinesulfinate decarboxylase inhibitor, to probe taurine and pyruvate synthesis.

Although several pathways contribute to the catabolism of L-cysteine, the products formed are few--taurine + CO2 and pyruvate + ammonia + sulfate. L-Cysteinesulfinate is a key intermediate that is either decarboxylated to ultimately yield taurine or transaminated to yield pyruvate. There is strong evidence that pyruvate is also formed by several cysteinesulfinate-independent pathways collectively referred to as "cysteine desulfhydrase." The quantitative importance of cysteinesulfinate-independent pathways of taurine synthesis is less clear, but it has been suggested that taurine synthesis from the cysteamine released during phosphopantetheine and CoASH turnover accounts for the high taurine content of tissues with very low levels of cysteinesulfinate decarboxylase activity (e.g. skeletal muscle and heart). In the present studies, the metabolic flux through each of these pathways was quantitated in vivo by monitoring the formation of respiratory 14CO2 in mice administered L-[1-14C]- or L-[3-14C]cyst(e)ine. Mice given 0.05 mmol/kg of L-cystine or 0.5 or 2.5 mmol/kg of L-cysteine catabolize 35, 51, and 72% of the dose, respectively, in 6 h; the relative contribution of taurine synthesis to total catabolism decreases from 63 to 51 to 42% as the L-cyst(e)ine dose is increased. To evaluate the role of L-cysteinesulfinate in taurine synthesis, D-cysteinesulfinate was characterized and used as a metabolism-resistant, potent, and specific inhibitor of cysteinesulfinate decarboxylase. Studies with L-[1-14C]- and L-[3-14C]cysteine in the presence of inhibitor indicate that 85-93% of taurine synthesis occurs from L-cysteinesulfinate: the calculated contribution of the phosphopantetheine pathway is small and may approximate zero. L-Cysteinesulfinate transmamination accounts for 25% of pyruvate synthesis from L-[14C]cystine (0.05 mmol/kg) but only 11% of pyruvate synthesis from L-[14C]cysteine (2.5 mmol/kg). Cysteine desulfhydrase reactions account for most of the pyruvate synthesis.

Animals↗
PubMed2003

Steady-state kinetics and molecular evolution of Escherichia coli MenD [(1R,6R)-2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase], an anomalous thiamin diphosphate-dependent decarboxylase-carboligase.

(1R,6R)-2-Succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) synthase, or MenD, catalyzes the thiamin diphosphate- (ThDP-) dependent decarboxylation of 2-oxoglutarate, the subsequent addition of the resulting succinyl-ThDP moiety to isochorismate, and the delta-elimination of pyruvate to yield SHCHC, pyruvate, and carbon dioxide. The enzyme is part of a superfamily of ThDP-dependent 2-oxo acid decarboxylases that includes pyruvate decarboxylase, benzoylformate decarboxylase, and acetohydroxy acid synthase, among others. However, this is the only enzyme known to catalyze a Stetter-like 1,4-addition of a ThDP adduct to the beta-carbon of an unsaturated carboxylate. Herein we report properties of the MenD protein from Escherichia coli, including the results of the first steady-state kinetic studies of the SHCHC synthase reaction. The protein is a dimer and shows cooperativity with respect to both substrates. The enzyme prefers divalent manganese as its metal ion cofactor and shows no dependence on FAD. MenD, required for biosynthesis of menaquinone and phylloquinone, is found in the genomes of a wide range of bacteria, as well as that of the archaeon Halobacterium sp. NRC-1 and the eukaryote Arabidopsis thaliana. Sequence alignments with other members of the superfamily are used to predict amino acid residues likely to be important in the binding and activation of ThDP. A site-directed mutant that replaces the conserved glutamic acid residue (E55), predicted to interact with N1' of the aminopyrimidine ring, with glutamine was generated, with catastrophic results for catalysis. There is no evidence for the release of succinate semialdehyde as a product; therefore, EC 4.1.1.71 should not be used for this enzyme.

Amino Acid Sequence↗