Peculiarities of Activation of Glycogenolysis Enzymes in Skeletal Muscles of the Trout Salmo trutta morpha Fario

Abstract

In skeletal muscles of the trout, a fish that intensively swims and is capable for sharp sprinting movements, an active form of ATP: phosphorylase b phosphotransferase (EC 2.7.1.38, glycogen phosphorylase kinase; GPK) and partially active 1,4-D-glucan:orthophosphate glucosyltransferase (EC 2.4.1.1, glycogen phosphorylase; GP) are revealed in the state of a relative rest. The isolated GP ab has a higher affinity to substrates (glucose-1-phosphate and glycogen) than GP b and is able to split glycogen without pre-activation with AMP or GPK. The presence of the activated forms of GPK and GP in resting muscles of the trout provides an opportunity for the very fast Ca2+-activation of glycogenolysis, coupled with activation of muscle contraction. This seems to be a biochemical mechanism of adaptation for the energy supply of intense muscle activity in this fish species inhabiting rapid cataracted rivers.