LINGCOD MUSCLE PURINE NUCLEOSIDE PHOSPHORYLASE

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Abstract
A purine nucleoside phosphorylase enzyme preparation, which catalyzed the general reaction ribose (deoxyribose)-l-phosphate+purine[image]purine nucleoside (deoxynucleoside)+orthophosphate, was isolated from muscles of the lingcod (Ophiodon elongatus). The reaction was found to be about 85% in favor of nucleoside synthesis with 10 [mu][image]/ml. concentrations of reactants in the hypoxanthine-inosine system. With similar concentrations of reactants in the guanine-guanosine system the equilibrium was about 75% in favor of nucleoside synthesis, and with considerably higher concentrations of reactants in this system this percentage decreased markedly. Purified preparations were stable for over a year at -20[degree]C, contained two major protein components (zone electrophoresis and ultracentrifuge data), were rather heat labile, and possessed a maximum activity corresponding to liberation of 32 [mu]. orthophosphate/mg. protein N/hour. Evidence is given in support of the view that a single enzyme is responsible for the above reaction and that it possesses strict specificity for [alpha]-D-ribofuranose 1-phosphate and deoxyribose 1-phosphate. Of a large number of substituted purines investigated, only the following were active: hypoxanthine, xanthine, 6-mercaptopurine, 6-methylpurine, 8-azaguanine, guanine, adenine, and 2,6-diaminopurine. Methods are given for the preparation, in good yield, of analytically pure dicyclohexylammonium salts of ribose 1-phosphate and deoxyribose 1-phosphate.