Metabolic enzyme activities, oxygen consumption and glucose utilization in sea raven (Hemitripterus americanus) erythrocytes

The organization of energy metabolism was assessed in erythrocytes of the sea raven (Hemitripterus americanus). Cell suspensions displayed a potential for aerobic glycolysis, shown by the presence of the glycolytic enzymes phosphofructokinase, aldolase and pyruvate kinase and the mitochondrial markers citrate synthase and malate dehydrogenase. Rates of oxygen uptake (Moo2) and glucose uptake Mglucose (as assessed by the disappearance of glucose) are closely matched in whole blood and resuspended erythrocyte preparations. Lactate does not accumulate under aerobic conditions. The enzymatic potential is well in excess of maximal rates of carbon flux in intact cells. Overall, the data reveal that sea raven erythrocytes have an aerobic metabolism that is fuelled by exogenous glucose. Calculated rates of glucose oxidation from [6-14C]glucose were 1000-fold lower than rates measured directly from glucose disappearance, implying that exogenous glucose is highly diluted or mixed into the intracellular pools prior to entry into the citric acid cycle.