Nature of the enzymes that catalyse the cleavage of the N-glycosidic bond of pyrimidine ribonucleosides in some filamentous fungi

Abstract

Cell-free extracts of nitrate-grown mycelia of Penicillin chrysogenum, Penicillin oxilicum and Fasarium moliforme have the ability to catalyse the cleavage of the N-glycosidic bond of cytidine and uridine optimally at pH 6.2 and 40°. The cleavage of these two nucleosides was effected by a contitutive pyrimidine ribonucleosides hydrolase, a pyrimidine ribonucleosides phosphorylase and a broad spectrum pyrimidine and purine ribonucleosides in extracts of P. chrysogenum, P. oxicalum and Fusarium monoliforme respectively. Deoxyribothymidine was not cleaved by any of these extracts under all the experimental conditioins used.