The generalization that 'when a metabolic sequence involves consecutive nicotinamide-adenine dinucleotide-dependent reactions, the dehydrogenases have the same stereospecificity' was tested and confirmed for three metabolic sequences. (1) NAD+-xylitol (D-xylulose) dehydrogenase and NADP+-xylitol (L-xylulose) dehydrogenase are both B-specific. (2) D-Mannitol 1-phosphate dehydrogenase and D-sorbi...

The serum levels of the mitochondrial enzymes), aspartate transatninase II, malate dehydrogenase II and glutamate dehydrogenase were studied in 82 cases of acute hepatitis. The activity ratio alanine transaminase/glutamate dehydrogenase and the C/M-ratios of aspartate transaminase and malate dehydrogenase were also studied. The serum levels of the mitochondrial en2ymes glutamate dehydrogenase, ...

Mitochondrial malate dehydrogenase shows a complex regulation pattern in the presence of citrate. Previously published results indicate that this enzyme is activated by citrate in the NAD(+)----NADH direction and inhibited in the opposite direction. Moreover, high concentrations of L-malate or oxaloacetate produce deviations from the Michaelis-Menten behaviour. Results reported in this paper cl...

A method to fractionate com (Zea mays L. B73) mitochondria into soluble proteins, high molecular weight soluble proteins, and membrane proteins was developed. These fractions were analyzed by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and assays of mitochondrial enzyme activities. The Krebs cycle enzymes were enriched in the soluble fraction. Malate dehydrogenase has been pu...

Seedlings of castor bean (Ricinus communis cv. Hale) were exposed to gibberellin A(3) (GA(3)) (100 micromolar) for periods up to 20 hours. Endosperm homogenates were fractionated on linear sucrose gradients and enzymes in mitochondria, glyoxysome, and cytosol fractions were assayed. Gibberellin treatment resulted in increases in the activities of enzymes in all three compartments. There were al...

The mechanism by which Helminthosporium maydis race T toxin inhibits respiration dependent on NAD(+)-linked substrates in T cytoplasm corn mitochondria was investigated. The toxin did not cause leakage of the soluble matrix enzyme malate dehydrogenase from the mitochondria or inhibit malate dehydrogenase or isocitrate dehydrogenase directly. The toxin did increase the permeability of the inner ...