EFFECT OF HYPOXIA ON THE ACTIVITY AND BINDING OF GLYCOLYTIC AND ASSOCIATED ENZYMES IN SEA SCORPION TISSUES

The effect of hypoxia on the levels of glycogen, glucose and lactate a s well as the activities and binding of glycolytic and associated enzy mes to subcellular structures was studied in brain, liver and white mu scle of the teleost fish, Scospaena porcus. Hypoxia exposure decreased glucose levels in liver from 2.53 to 1.70 mu mol/g wet weight and in muscle led to its increase from 3.64 to 25.1 mu mol/g wet weight. Maxi mal activities of several enzymes in brain were increased by hypoxia: hexokinase by 23%, phosphoglucoisomerase by 47% and phosphofructokinas e (PFK) by 56%. However, activities of other enzymes in brain as well as enzymes in liver and white muscle were largely unchanged or decreas ed during experimental hypoxia. Glycolytic enzymes in all three tissue s were partitioned between soluble and particulate-bound forms. In sev eral cases, the percentage of bound enzymes was reduced during hypoxia ; bound aldolase in brain was reduced from 36.4 to 30.3% whereas gluco se-6-phosphate dehydrogenase fell from 55.7 to 28.7% bound. In muscle PFK was reduced from 57.4 to 41.7% bound. Oppositely, the proportion o f bound aldolase and triosephosphate isomerase increased in hypoxic mu scle. Phosphoglucomutase did not appear to occur in a bound form in li ver and bound phosphoglucomutase disappeared in muscle during hypoxia exposure. Anoxia exposure also led to the disappearance of bound fruct ose-1,6-bisphosphatase in liver, whereas a bound fraction of this enzy me appeared in white muscle of anoxic animals. The possible function o f reversible binding of glycolytic enzymes to subcellular structures a s a regulatory mechanism of carbohydrate metabolism is discussed.