Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.8.1.4 (diaphorase)
 2,754 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adult Hymenolepis diminuta mitochondria catalyze a transhydrogenation reaction between NADPH and NAD and between NADH and NAD. The NADPH-->NAD reaction is catalyzed by an inner membrane-associated pyridine nucleotide transhydrogenase, whereas the NADH-->NAD reaction is ostensibly catalyzed by another system(s). The source(s) of NADH-->NAD activity was evaluated by assessments of its intramitochondrial distribution and thermal lability and by comparisons with the distribution/thermal lability of NADH dehydrogenase, lipoamide dehydrogenase, and NADPH-->NAD transhydrogenase. The occurrence of NADH and lipoamide dehydrogenase components was readily demonstrable. Like NADPH-->NAD transhydrogenase, NADH dehydrogenase was essentially membrane bound. Lipoamide dehydrogenase and NADH-->NAD activities were, at different levels, in the membrane and soluble fractions. Based on thermal profiles, NADH and lipoamide dehydrogenase differed from each other and from NADPH-->NAD transhydrogenase. Although the NADH-->NAD profile closely paralleled that for lipoamide dehydrogenase, it also was similar to the NADH dehydrogenase profile. Collectively, these data are consistent with the supposition that the H. diminuta mitochondrial NADH-->NAD transhydrogenation reaction is catalyzed by lipoamide dehydrogenase and possibly by NADH dehydrogenase rather than by an independent transhydrogenase system.
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PMID:Mitochondrial NADH-->NAD transhydrogenation in adult Hymenolepis diminuta. 777 19

Transhydrogenase and diaphorase activity of ferredoxin-NADP reductase are enhanced by plant ferredoxins. This stimulation is specific; ferredoxin cannot be replaced by sulfhydryl compounds such as cysteine or dithiothreitol, the apoprotein of ferredoxin or Fe(2+), Fe(3+) ions.The effect is particularly obvious with the reductase from the heterokont algaBumilleriopsis filiformis Vischer.Reductase and ferredoxin form a complex in the molar ratio of 1:1, which is sensitive to high ionic strength. Under these conditions the complex is destroyed thus eliminating the enhancement by ferredoxin of both transhydrogenase and diaphorase activities. It is concluded that the effect is due to complex formation.Higher concentrations of NAD (>3 mM) and of NADPH (>0.01 mM) inhibit transhydrogenase activity without any effect on its enhancement by ferredoxin. A specific binding site on the reductase for ferredoxin is assumed for which NAD is a poor competitor. Only in the absence of ferredoxin does NAD seem to activate the reductase by occupying both the ferredoxin site and that of the pyridine nucleotides. Reaction kinetics (as a function of NAD concentration) therefore switch from a sigmoid shape when no ferredoxin is added to the normal hyperbolic shape in its presence. Kinetic studies further suggest a "ping pong" type reaction mechanism for the transhydrogenase and diaphorase reaction. A possible change of the underlying mechanism in the presence of ferredoxin is discussed.
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PMID:[Influence of ferredoxin on ferredoxin-NADP reductase]. 2448 83