Purification and characterization of an aminopeptidase from bovine cornea

An aminopeptidase from bovine cornea has been extensively purified by gel filtration and ion-exchange chromatography. The purified enzyme with a molecular weight of 96,000 showed broad substrate specificity. All of the various aminoacyl bonds were hydrolyzed optimally at pH 6.5. The purified enzyme showed hydrolytic activity towards bioactive peptides such as enkephalins, bradykinin, and angiotensin-II. The enzyme was inhibited by bestatin, amastatin, puromycin, bacitracin, sulfhydryl reagents and metal chelators. Only Co2+ stimulated the enzyme whereas other heavy metal ions were toxic. The gross properties of the corneal enzyme resemble those of an aminopeptidase III isolated from bovine lens.