GLYCOLYTIC CONTROLS IN ESTIVATION AND ANOXIA - A COMPARISON OF METABOLIC ARREST IN LAND AND MARINE MOLLUSKS

Facultative metabolic rate depression is the common adaptive strategy underlying various animal mechanisms for surviving harsh environmental conditions. This strategy is common among molluscs, enabling animals to survive over days or even months in the absence of oxygen or under extremely dry conditions. The large reductions in metabolic rate durin g estivation and anoxia can translate into considerable energy savings when dormant animals are compared to active animals. A complex metabo lic coordination is required during the transition into the dormant st ate to maintain cellular homeostasis and involves both energy-consumin g and energy-producing pathways. With regard to energy-producing pathw ays, several different mechanisms have been identified that participat e in controlling flux. One such mechanism, enzyme phosphorylation, can have a wide-ranging effect. For example, phosphorylated enzymes exhib it altered substrate, activator, and inhibitor affinities. This effect may be magnified by changes in the concentrations of allosteric effec ters, such as fructose 2,6-bisphosphate, that occur during hypometabol ic states. Changes in fructose 2,6-bisphosphate are related to changes in enzyme phosphorylation through changes in the relative activity of phosphofructokinase-2. Alterations in glycolytic enzyme binding can a lso be brought about through changes in enzyme phosphorylation. The pr esent review focuses on identifying hypometabolism-related changes in enzyme phosphorylation as well as characterizing the mechanisms involv ed in mediating these phosphorylation events. (C) 1997 Elsevier Scienc e Inc.