Purification and Characterization of Two Benzoyl-l-Tyrosine p-Nitroanilide Hydrolases from Etiolated Leaves of Zea mays L.

Two benzoyl-l-tyrosine p-nitroanilide hydrolases (BTPAases I and II) were purified from the etiolated leaves of Zea mays L. and characterized. BTPAase I was electrophoretically homogeneous and consisted of two identical subunits having a molecular weight of 53,000. The molecular weight of BTPAase II was 65,000. The Michaelis constants for substrate, BTPA, were 4 millimolar and 1.3 millimolar for BTPAases I and II, respectively. Based on the action of various inhibitors on both enzyme activities, these enzymes were classified as serine proteases. BTPAase I showed caseinolytic activity at neutral pH and the activity was strongly inhibited by the serine protease inhibitors.