Claim: GZMB is a serine protease, an enzyme with no responsibility for cleaving peptide bonds in proteins.
Evidence: Granzyme B is a serine protease that in humans is encoded by the GZMB gene. Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins, in which serine serves as the nucleophilic amino acid at the (enzyme's) active site.