FACULTATIVE ANAEROBIOSIS IN HALIOTIS (ORMER ABALONE) - PYRUVATE-KINASE AND PHOSPHOENOLPYRUVATE CARBOXYKINASE ACTIVITIES

The pH profile for pyruvate kinase is sharp. This enzyme is similar to L-type enzymes; it is sigmoidal with respect to phosphoenolpyruvate, activated by FDP [fructose-1,6-diphosphate] and is inhibited by L-alanine. Depending upon the state of tidal exposure, the substrate vs. velocity data were best fitted to a Michaelis-Menten or a Hill Model for pyruvate kinase with phosphoenolpyruvate. The extremely high K0.5S value for the emerged state approximates inhibition by L-alanine. Pyruvate kinase to phosphoenolpyruvate carboxykinase activity ratios correlate broadly with known vertical zonations for 4 spp. of Haliotis [H. rufescens, H. cracherodii, H. fulgens and H. corrugata].