Enzymes of Nucleic Acid Metabolism from Mung Bean Sprouts

Several enzymes involved in nucleic acid metabolism, phosphomonoesterase, ribonuclease M1, 3'-nucleotidase, deoxyribonuclease, and ribonuclease M2, were partially purified from mung bean sprouts. The phosphomonoesterase was separated from the other enzymes and purified 130-fold. It was shown to be nonspecific, with a pH optimum of 6.5. RNase M1 was fractionated from the other types of enzymes by two methods, one of which resulted in a 200-fold purification. Its action on ribonucleic acid was shown to produce a mixture of 2', 3'-cyclic nucleotides; the cyclic purine nucleotides were further hydrolyzed to 3'-phosphates, while the cyclic pyrimidine nucleotides were not. The enzyme was found to be stable to dialysis at pH 5, and to have optimum activity near pH 5.5. 3'-Nucleotidase, RNase M2, and DNase, which were present in a common fraction, were purified about 50-fold. Unlike the 3'-nucleotidase and RNase M2 activities, the DNase activity declined considerably upon standing, and was therefore considered to be due to a unique enzyme. The specificities and other properties of the 3'-nucleotidase and RNase M2 are reported in two accompanying papers.