Occurrence of Methylated Purine Bases in Yeast Ribonucleic Acid*

A number of methylated purine bases have recently been reported to occur in small quantities in the urine of normal human subjects. These include 1-methylguanine, iV*-methylguanine (6-hydroxy-2-methylaminopurine) ,I 1-methylhypoxanthine, and 8-hydroxy-7-methylguanine (1) in addition to 7-methylguanine, previously known as a urinary constituent (2). These compounds were found to be metabolites of endogenous origin (3). Their metabolic role has not been elucidated. The present study was undertaken to determine whether some of these methylated purines may occur as minor components of nucleic acids. Because of their ready availability, preparations of yeast ribonucleic acid and deoxyribonucleic acids from calf thymus and herring sperm were first examined.