Copyright ©) 1993, American Society for Microbiology NOTES Identification of an Intracellular Pyrimidine-Specific Endoribonuclease from Bacillus subtilis

Two intracellular RNases which were easily separated by fractionation on strong anion- or cation-exchange resins were identified from Bacillus subtilis. One cleaved any phosphodiester bond, while the second cleaved only pyrimidine-N bonds. The enzyme with pyrimidine-N specificity was-15 kDa, had a pH optimum of-6.2, degraded C-C bonds-10 times faster than U-U bonds, and was completely inactive against single-stranded DNA. The enzyme is called RNase C and may be the first reported broad-specificity endoribonuclease from B. subtilis. Ribonucleases participate in both anabolic and catabolic processes of metabolism. In Escherichia coli the endoribo-nucleases (endoRNases) are divided enzymologically into two distinct groups. Those RNases concerned with processing precursor RNA (processing RNases) have stringent substrate specificities and generate 5'-P, 3'-OH ends upon cleavage while the degradative endoRNases have broad substrate spec-ificities and generate 5'-OH, 3'-P ends upon cleavage (5). A few degradative endoRNases have been identified from th