Search results for "hydrogenase"

Roles of sorbitol and sucrose in growth and respiration of ‘Encore’ peach fruit in the three developmental stages

2002

In peach [Prunus persica (L.) Batsch (Peach Group)], both sorbitol and sucrose are utilized for source to sink carbon (C) transport, yet their specific functions in fruit growth and development remain unclear. Growth rate (GR), respiration rate (R), carbohydrate content, and the activities of sorbitol dehydrogenase (SDH), sorbitol oxidase (SOX), sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) were determined in ‘Encore’ peach fruit to study the specific functions of sorbitol and sucrose in each phase of fruit development (an early period of rapid cell division, a relatively inactive intermediate stage where endocarp (pit) hardening occurs, and a final swelling due to …

Screening of Ovarian steroidogenic pathway in Ciona intestinalis and its modulation after Tributyltin exposure

2010

In this study, we have identified several ovarian steroids in Ciona with high similarity to vertebrate steroids and showed that cholesterol, corticosterone, dehydroepiandrosterone, estrone, estradiol-17beta, testosterone, pregnenolone, progesterone, have identical molecular spectra with vertebrate steroids. In addition, we have studied the effects of an endocrine disruptor (tributyltin: TBT) on these sex hormones and their precursors, ovarian morphology, and gene expression of some key enzymes in steroidogenic pathway in the ovary of Ciona. Ovarian specimens were cultured in vitro using different concentrations of TBT (10{sup -5}, 10{sup -4} and 10{sup -3} M). Ethanol was used as solvent co…

The effects of a 3-week training on basal biomarkers in professional soccer players during the preseason preparation period

2012

Intracellular compartmentation and regulation of two shikimate dehydrogenase isoenzymes in Pisum sativum

1974

Summary Pea seeds as well as sprouts and roots contain two isoenzymes of shikimate dehydrogenase. Both isoenzymes can be separated by Polyacrylamide gel electrophoresis as well as through ammonium sulfate fractionation. The molecular weight of both isoenzymes are the same although the net electric charge is different. The Km value for isoenzyme 1 is 3,5 × 10 −4 and the Km value for isoenzyme 2 is 1,67 × 10 −4 M. 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, gallic acid, anthranilic acid and p-methoxycinnamic acid inhibited both isoenzymes competitively. Anthranlic acid showed the largest affinity to both isoenzymes. M-methoxycinnamic acid and m-nitrocinnamic acid inhibited both isoe…

Candida albicans TDH3 gene promotes secretion of internal invertase when expressed in Saccharomyces cerevisiae as a glyceraldehyde-3-phosphate dehydr…

2003

We have checked the ability of the Candida albicans GAPDH polypeptide, which lacks a conventional N-terminal signal peptide, to reach the cell wall in Saccharomyces cerevisiae by using an intracellular form of the yeast invertase as a reporter protein. A hybrid TDH3-SUC2 gene containing the C. albicans TDH3 promoter sequences and a coding region encoding a fusion protein formed by the C. albicans GAPDH polypeptide, fused at its C-terminus with the yeast internal invertase, was constructed in a centromer derivative plasmid and transformed into a Suc(-) S. cerevisiae strain. Transformants displayed invertase activity measured in intact whole cells, and were able to grow on sucrose as the sole…

Bacterial 2,3-butanediol dehydrogenases

1978

Enterobacter aerogenes, Aeromonas hydrophila, Serratia marcescens and Staphylococcus aureus possessing L(+)-butanediol dehydrogenase produced mainly meso-butanediol and small amounts of optically active butanediol; Acetobacter suboxydans, Bacillus polymyxa and Erwinia carotovora containing D(-)-butanediol dehydrogenase produced more optically active butanediol than meso-butanediol. Resting and growing cells of these organisms oxidezed only one enantiomer of racemic butanediol. The D(-)-butanediol dehydrogenase from Bacillus polymyxa was partially purified (30-fold) with a specific activity of 24.5. Except NAD and NADH no other cofactors were required. Optimum pH-values for oxidation and red…

Influence of inorganic pyrophosphate on the kinetics of muscle pyruvate kinase: a simple nonallosteric feedback model.

2002

Potassium pyrophosphate was used instead of ATP as a model ligand for magnesium cation for the study of effector influence on the kinetics of pyruvate kinase muscle isozyme M1. The pyruvate kinase activation by low concentration of pyrophosphate and inhibition by high concentration of pyrophosphate was considered to be the result of reversible reactions of magnesium cation with pyrophosphate, ADP, ATP, and PEP. The apparent Km and Vm or in some cases the pseudo-first order reaction rate constant (instead of Km and Vm) of pyruvate kinase at any given pyrophosphate concentration were analysed as a function of concentration of free magnesium cation and its complexes with all ligands present in…

A hypothetical model of the influence of inorganic phosphate on the kinetics of pyruvate kinase

2000

This paper presents a simple solution to the problem of approximating the calculated curve of reaction progress to the measured curve which is usually disturbed by initial oscillation of auxiliary lactate dehydrogenase (LDH) reaction. The experiments leading to the determination of the apparent Km for phosphoenolpyruvate (PEP) and Vm were performed. For precise estimation of kinetic parameters (Km and Vm) of the M1 isozyme of pyruvate kinase (PK), measured by coupling it to LDH reaction, the sequence of Michaelis‐Menten for pyruvate kinase and second-order kinetics for lactate dehydrogenase reaction as well as a non-zero initial concentration of lactate was assumed. The functions of apparen…

Cherimolin-1, New Selective Inhibitor of the First Energy-Coupling Site of the NADH:Ubiquinone Oxidoreductase (Complex I)

1997

The mechanism linking electron transport to proton translocation in the NADH:ubiquinone oxidoreductase (complex I of the mitochondrial respiratory chain) is still unclear. Inhibitors acting at different sites of the enzyme are powerful tools to clarify this mechanism. Up to now, a unique inhibitor, the Annonaceous acetogenin rolliniastatin-2, selectively blocks the most internal proton-translocation site. This study introduces cherimolin-1, a new acetogenin that inhibits the complex I with this special mode of action, which is more easily available from the plant material. Moreover, the mode of action of this scarce type of complex I inhibitor is further characterized.

Increased dynamic effects in a catalytically compromised variant of Escherichia coli dihydrofolate reductase

2013

Isotopic substitution (15N, 13C, 2H) of a catalytically compromised variant of Escherichia coli dihydrofolate reductase, EcDHFR-N23PP/S148A, has been used to investigate the effect of these mutations on catalysis. The reduction of the rate constant of the chemical step in the EcDHFR-N23PP/S148A catalyzed reaction is essentially a consequence of an increase of the quasi-classical free energy barrier and to a minor extent of an increased number of recrossing trajectories on the transition state dividing surface. Since the variant enzyme is less well set up to catalyze the reaction, a higher degree of active site reorganization is needed to reach the TS. Although millisecond active site motion…