Specificity and properties of wheat-germ esterase

Singer & Hofstee (1948a, b) studied an enzyme from wheat germ, 'wheat-germ lipase', that hydrolysed glyceryl and aliphatic esters. Gowron, Grelecki & Duggan (1953) investigated the hydro- lysis of aromatic esters by the same enzyme. Jansen, Nutting & Balls (1948) showed that certain plant enzymes, including that from wheat germ, would hydrolyse glyceryl, aromatic and choline esters. Since acetates were cleaved more rapidly than esters of higher acid homologues, they called these enzymes acetylesterases. Plant acetyl- esterases were inhibited by organophosphorus compounds (Jansen et al. 1948; Mounter, Tuck, Alexander & Dien, 1957). It is apparent that this hydrolytic enzyme of wheat germ has several points of similarity to other esterases, cholinesterases and lipases. However, in a number of specificity studies true maximal velocities of enzymic reactions have not been obtained and many experiments with hydrolytic enzymes have been limited by the use ofreadily soluble substrates. The kinetics of certain esterases and lipases in heterogeneous systems have been discussed by Aldridge (1954). Desnuelle (1961) has studied the properties of highly purified pancreatic lipase and the kinetics of hydrolysis of emulsions of sparingly soluble esters. Additional data for the establish- ment of distinctions between esterases and lipases are desirable. In the present investigation, the rates of hydrolysis of a number of esters by wheat-germ esterase have been studied.