Phosphate-stimulated breakdown of 5'-methylthioadenosine by rat ventral prostate.

A soluble enzyme preparation catalysing the release of adenine from 5'-methylthioadenosine was purified some 30-fold from extracts of the rat ventral prostate. This reaction was completely dependent on addition of inorganic phosphate ions to the assay medium. This absolute requirement for phosphate ions suggests a phosphorolytic cleavage mechanism. After acid treatment, the other product of the reaction appeared to be 5-methylthioribose. The actions of some other well-characterized enzymes of nucleoside metabolism of 5'-methylthioadenosine were also investigated; purified purine nucleoside phosphorylases from calf spleen and human erythrocytes did not attack 5'-methylthioadenosine. The role of 5'-methylthioadenosine in mammalian tissues is discussed.