RNase H type-1 (PS50879) The ribonuclease H (RNase H) (EC 3.1.26.4), which is part of the ribonuclease family, can find and cut the RNA strand in RNA-DNA heteroduplexes. RNase HI is the primary source of RNH activity. All LTR retrotransposons have acquired an enzymatically feeble RNase H domain, devoid of the critical catalytic residues present in all other RNase H enzymes. All RNase H domains have the same catalytic residues for enzyme activity. These are made up of three aspartic acid residues and one glutamic acid residue.