MODIFICATION OF PYRUVATE-KINASE AND LACTATE-DEHYDROGENASE IN FOOT MUSCLE OF THE SEA MUSSEL MYTILUS-GALLOPROVINCIALIS UNDER ANAEROBIOSIS ANDRECOVERY

The modification of pyruvate kinase (PK) and lactate dehydrogenase (LD H) activity in foot muscle of the mussel Mytilus galloprovincialis dur ing exposure to air and recovery in water was investigated. In the cou rse of exposure to air, the activity of these enzymes measured at high and low substrate concentrations showed successive increases and decr eases. Returning the mussels to water after exposure to air affected e nzyme activity in a manner similar to anaerobiosis. When measuring at saturated concentrations of substrates and substrate and coenzyme for PK and LDH, respectively, the maximum activation of PK (37%) was obser ved at 4 h of animal exposure to air, and for LDH (67%) at 6 h exposur e to air. During 24 h of exposure of animals to air, PK activity pract ically reached the stock level, while LDH was still activated (148%). The change in lactate dehydrogenase activity in mussel muscle during a noxia and recovery is described here for the first time. Variation in pyruvate kinase activity during exposure to air and recovery is linked to the alteration of half-maximal saturation constants and maximal ve locity for both substrates. The possible role of reversible phosphoryl ation in the regulation of pyruvate kinase and lactate dehydrogenase p roperties is discussed.