Oxidative phase of pentose-phosphate cycle in sea mussel (mytilus edulis l.)

Abstract

Glucose-06-phosphate dehydrogenase (E.C. 1.1.1.49) and 6-phosphogluconate dehydrogenase (E.C. 1.1.1.44) activities measured in tissue extracts from sea mussel exhibit a potential unbalance which could cause an accumulation of 6-phosphogluconate. Nevertheless elevated levels of this metabolite are not detected in mussel tissues. The Entner-Doudoroff pathway has not been found in hepatopancreas, adductor muscle and gill tissues. Hepatopancreas glucose-06-phosphate-dehydrogenase and 6-phosphogluconate dehydrogenase apparent kinetic parameters at 25 degrees C, were determined. The enzymes are competitively inhibited by NADPH with respect to NADP+. Oxidized Glutathione at nearly physiological concentrations counteracts NADPH inhibition.