ALTERATION OF KINETIC-PROPERTIES OF PYRUVATE-KINASE IN PHASCOLOSOMA-ARCUATUM (SIPUNCULIDA) EXPOSED TO ENVIRONMENTAL ANOXIA

After 48 h of exposure to environmental anoxia, the kinetic properties of pyruvate kinase (PK) in the local sipunculid worm Phascolosoma arcuatum were altered. However, no change in the kinetic properties of phosphoenolpyruvate carboxykinase was observed. The modified PK extracted from the whole body of the anoxic worm had a lower apparent affinity for phosphoenolpyruvate compared to the PK extracted from the aerobic worms. Results of cellulose acetate electrophoreses and isoelectric focusing revealed the presence of three distinct PK isozymes in P. arcuatum. The kinetic and physical properties of the PK isozymes in the body wall and the proboscis cum attached retractor muscles, but not those of the PK in the digestive tract, were altered during anoxia. Results obtained from treating the PK in the extracts from the anoxic worms with alkaline phosphatase in vitro indicate that anoxia-induced phosphorylation of PK occurs in P. arcuatum.