The Enzyme 5-Phosphorylribose Pyrophosphokinase in Fish Muscle

The enzyme 5-phosphorylribose pyrophosphokinase was found in the muscles, and in certain of the organs, of marine teleost fish. It was considerably purified at between 0 and −1 °C by a simple, rapid procedure which involved extraction of the muscle with water, precipitation of the active fraction at pH 5.5, re-solution of the precipitate in 0.1 M phosphate buffer pH 7.0, and removal of about half the inactive protein from the solution by treatment with alumina Cγ gel. The enzyme was found to be very unstable, purified preparations losing activity quite rapidly even when stored at less than −50 °C. The requirement of the enzyme for ATP, R5P, Mg++, and glutathione, and its pH–activity relationship, were investigated. The lithium salt of PRPP was prepared in good yield and in a comparatively high state of purity using the purified muscle enzyme from lingcod.