PMID: 39065Jul 1, 1979

Differences between the reactivities of two pyridine nucleotides in the rapid reduction process and the reoxidation process of adrenodoxin reductase

Journal of Biochemistry
T SugiyamaT Yamano

Abstract

The reaction process of adrenodoxin reductase with NADPH and NADH were investigated. The appearance of new intermediate with a broad absorption band at around 520 nm has been detected by rapid-scan stopped-flow spectrophotometry. Although the formation of this intermediate is more rapid with NADPH than with NADH, the rates of the subsequent decay to the fully reduced state are almost identical (Kobs values were 20.5 and 16.0s-1). These results indicate that the new intermediate is the complex formed between the oxidized enzyme and reduced pyridine nucleotide (enzyme-substrate complex), and that subsequent decay of the intermidiate is caused by a two-electron transfer process from the reduced pyridine nucleotide to the enzyme flavin. On the other hand, spectral and kinetic properties in the steady state of the reoxidation reaction of the enzyme reduced with NADPH and NADH were somewhat different. The rate of reoxidation of the enzyme under aerobic conditions from the reduced state to the oxidized state was 6.5 times faster when a 10-fold molar excess of NADH was used than when NADPH of the same concentration was used. This result is consistent with the fact that the NADH-dependent oxidase activity was 6.4 times greater than that...Continue Reading

Related Concepts

FDXR
Ferredoxin-NADP Reductase
NADH
Mitochondria
Spectrophotometry
NADP
Oxygen Consumption
NADH, NADPH Oxidoreductases
DECR1
Oxidation-Reduction

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