metalloendopeptidase activity obsolete O-sialoglycoprotein endopeptidase activity true OBSOLETE. Catalysis of the hydrolysis of O-sialoglycoproteins; cleaves the -Arg31-Asp32- bond in glycophorin A. Does not cleave unglycosylated proteins, desialylated glycoproteins or glycoproteins that are only N-glycosylated. This term was made obsolete because it represents a gene product. glycoprotease activity sialoglycoproteinase activity molecular_function O-sialoglycoprotein endopeptidase activity sialoglycoprotease activity GO:0008450 glycophorin A proteinase activity glycoproteinase activity