Myeloblastin

Myeloblastin (, leukocyte proteinase 3, leukocyte proteinase 4, Wegener's granulomatosis autoantigen, proteinase PR-3, proteinase-3, PMNL proteinase) is an enzyme. This enzyme catalyses the following chemical reaction: Hydrolysis of proteins, including elastin, by preferential cleavage: -Ala- >  -Val-

This enzyme is present in polymorphonuclear leukocyte granules. Downregulation of myeloblastin in promyelocytic leukemia cells was shown to induce their growth arrest and differentiation.