Anaerobic energy metabolism in the tail musculature of the Australian yabby Cherax destructor (crustacea, decapoda, parastacidae). Regulation of anaerobic glycolysis

Abstract

1. 1. During bursts of rapid tail flipping by the yabby Cherax destructor, arginine phosphate reserves are depleted and energy charge falls before lactate starts to accumulate in the tail musculature. Regulation of anaerobic glycolysis in this muscle was investigated by examining the effects of arginine phosphate, adenylates and pH on the properties of the glycolytic enzymes phosphofructokinase, pyruvate kinase and lactate dehydrogenase. 2. 2. Phosphofructokinase was purified 60-fold. The enzyme was insensitive to physiological concentrations of arginine phosphate. Of the adenylates, AMP had the most marked effect by converting the fructose-6-phosphate saturation curve from sigmoidal to hyperbolic, resulting in a large decrease in K m/ S 0.5 fructose-6-phosphate. Enzyme activity decreased markedly below pH 7.0. 3. 3. Pyruvate kinase was purified 63-fold. While the properties of the enzyme were not influenced by arginine phosphate, they were strongly affected by physiological concentrations of ATP and ADP. ATP inhibition was partially removed by fructose-1,6-diphosphate. 4. 4. At pH values above 7.0 yabby tail muscle lactate dehydrogenase displayed properties typical of the vertebrate LDH M 4 isoenzyme. However, at pH 6.5, substrate inhibition by pyruvate increased and K m pyruvate was reduced, so that the enzyme displayed properties typical of the vertebrate LDH H 4 isoenzyme. 5. 5. It is proposed that the effects of changes in adenylate concentrations and/or pH on the properties of phosphofructokinase, pyruvate kinase and lactate dehydrogenase could be involved in regulatory glycolysis in yabby tail muscle.