In view of the increasing interest in the biochemistry of fish and particularly fish enzymes, a study has been made of some of the glycolytic enzymes of fish muscle. Some important properties of two enzymes of the Embden-Meyerhof pathway, phosphoglucomutase and phosphoglucose isomerase, and one enzyme of the "hexosemonophosphate shunt", phosphoribomutase, are reported. The procedure for purifying these enzymes by ammonium sulfate precipitation, heating or chromatography on diethylaminoethyl cellulose, is given. However, most of the experiments were carried out with crude extracts, since the partially purified enzymes were not very stable under the usual conditions of storage of enzymes. The following properties of phosphoglucomutase and of phosphoribomutase are reported: equilibrium of the reaction, optimum pH, requirement for magnesium and cysteine, and the effect of glucose-1,6-diphosphate, ribose-1,5-diphosphate and deoxyribose-1,5-diphosphate on its activity. A study of the equilibrium and optimum pH of the phosphoglucose isomerase reaction is also reported. The similarity between the properties of these fish enzymes and the corresponding ituunmalian enzymes is discussed. The question of identity or non-identity of phosphoglucomutase and phosphoribomutase is also examined. / Science, Faculty of / Zoology, Department of / Graduate