Anaerobiosis and organ-specific regulation of glycolysis in a marine whelk

Abstract

Changes in the levels of glycolytic intermediates, adenylates, phosphagen, and substrates and products of anaerobic metabolism were monitored over the initial hours of anaerobiosis in radular retractor muscle, foot muscle, and gill of the marine whelk Busycotypus canaliculatum. In all organs, changes in glycolytic intermediates upon exposure to N2-bubbled seawater indicated a biphasic response by glycolytic rate to anoxia: an immediate activation (within 30 min to 1 h) followed after 1–4 h by glycolytic rate depression. In both cases, regulatory control at phosphofructokinase and pyruvate kinase was indicated. The accumulation of anaerobic end products differed between the three organs. In radular retractor and gill, the ratio alanine succinate produced was 2:1 (but with higher amounts of both products in radular retractor), whereas in foot the ratio was 12.5:1. Foot muscle showed a large depletion of arginine phosphate reserves early in anoxia but little perturbation of adenylate pools, whereas gill and radular retractor showed a much lower net use of phosphagen but substantial depletion of organ ATP content. The data support several conclusions: (i) metabolic rate depression in the whelk is initiated within 1–2 h of anoxia exposure, (ii) mechanisms of metabolic depression override allosteric activating effects by phosphagen and adenylates on phosphofructokinase, and (iii) inhibition of flux through pyruvate kinase parallels the course of metabolic depression, not changes in carbon partitioning at the phosphoenolpyruvate branch point.