Ribonuclease H cleaves the RNA component of an RNA-DNA hybrid, a paired structure containing one RNA strand and one DNA strand. Its substrate recognition therefore concerns both chemical composition and pairing, rather than merely the presence of RNA anywhere in a sample.[ref]
Ribonuclease H in IUBMB Enzyme Nomenclature. EC 3.1.26.4, endonucleolytic cleavage and hybrid substrate
A 1973 calf-thymus study purified the enzyme more than three thousandfold and tested several substrates. It cleaved an artificial DNA/RNA polymer pair and a hybrid made with phage DNA, while the tested ribosomal RNA was not attacked. Activity also required a suitable metal ion.[ref]
Purification and properties of ribonuclease H of calf thymus by J. G. Stavrianopoulos and others. Abstract, purification, substrates and metal-dependent activation
The comparison illustrates a specificity test. Detecting cleavage in one preparation would show activity, while testing alternative substrates helps establish what the activity recognizes. Conversely, failure to cleave a hybrid under conditions lacking an activating ion would not establish that the hybrid is intrinsically resistant. Protein purification, substrate controls and assay conditions jointly support the molecular interpretation; the behavior of one preparation should not be assumed to specify every member of the broader enzyme family.
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Ribonuclease H (RNase H) is an enzyme that plays a crucial role in RNA metabolism. It specifically recognizes and degrades RNA strands that are hybridized to DNA. This characteristic makes RNase H important for various biological processes, including DNA replication, repair, and the removal of RNA primers during DNA synthesis.