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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4029

Mahendra K. Mohanty, Frissell R. Hunter, and Joseph B. Myers; Reduced Pyridine Nucleotide Oxidases of Euglena gracilis var. bacillaris. J.Protozool. 24(2):335-340, 1977

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Cell-free extracts of a streptomycin-bleached strain of Euglena gracilis var. bacillaris have been examined for enzyme systems primarily responsible for the oxidation of reduced pyridine nucleotides. NADH lipoyl dehydrogenase, NADH and NADPH oxidase, NADH and NADPH diaphorase, and NADH and NADPH cytochrome c reductase have been demonstrated. The NADPH-linked enzymes had lower activity rates and were less sensitive to N-ethyl maleimide and p-hydroxymercuribenzoate than their NADH-linked counterparts. NADH cytochrome c reductase was the most sensitive to antimycin A. Michaelis-Menten constants (Km) determined were as follows: NADH diaphorase, 350 µM; NADPH diaphorase, 200 µM; NADH cytochrome c reductase, 13 µM; NADPH cytochrome c reductase, 9 µM; NADH oxidase, 100 µM; NADPH oxidase 150 µM; NADH lipoyl dehydrogenase, 0.35 µM. Enzyme activities after storage at -5 degrees C indicate that the diaphorases are less labile than the other tested enzymes, and the differential activities of the NADH and NADPH linked enzymes suggest that funtionally they may have different roles.