Purification and properties of proteinase A from yeast

Proteinase A (EC 3.4.23.6) was purified from commercial bakers' yeast in five steps, including hydrophobic chromatography and affinity chromatography. After the last step the enzyme appeared homogeneous on polyacrylamide gel electrophoresis and in the analytical ultracentrifuge. A molecular weight of 41,500 was determined for proteinase A. The amino acid composition includes 43% polar residues and 12% aromatic amino acids. Proteinase A is a glycoprotein containing 7.5% mannose and 1% of glucosamine and galactosamine. The temperature and the pH stability of the enzyme have been determined. At pH 6, the proteinase exhibits a remarkable stability even in 6 M urea. Proteinase A splits hemoglobin with an optimum at pH 3.0 and casein and azocasein with an optimum at pH 6.0. The enzyme is inhibited by pepstatin, diazoacetyl-DL-norleucine methyl ester and by 1,2-epoxy-3-(4-nitro-phenoxy) propane.