Echinococcus multilocularis: comparative study of glycogen synthase in metacestodes and in the livers of infected and control Meriones unguiculatus

Abstract

A comparative study of the kinetic parameters of glycogen synthase was performed on Echinococcus multilocularis metacestodes and on the livers of infected and control host (Meriones unguiculatus). The enzyme of the parasite was found to be different from the enzyme of infected host liver. The apparent Km for UDP-glucose is 100 microM for the parasite and 400 microM for the host liver. The apparent Km for glucose 6-phosphate is 4 mM for the parasite and 2 mM for the host liver. The apparent Km for glycogen is 16 mg/ml for the parasite and 125 mg/ml for the host liver. The influence of glucose 6-phosphate and exogenous glycogen on the activity of glycogen synthase differs between the metacestode and the host liver. The enzyme of the metacestodes apparently does not need exogenous glycogen to work, contrary to the case for the liver host enzyme. The glycogen synthase of the parasite seems to be present in forms I and D, whereas the enzyme of the host liver appears in form I and that of the control liver in form D.