RNase T1

a nuclease that endonucleolytically cleaves ribonucleic acids at the 3′-5′ link of a guanosine 3′-phosphate residue, producing oligonucleotides terminating in this nucleotide; a transferase (endonuclease) in the first (cyclizing) step, a phosphodiesterase on the second (hydrolyzing) step. SYN: guanyloribonuclease, RNase N1.