Studies of proteolytic systems with synthetic dipeptides
Trew, John Allan
The production of wheat for flour is the industry of the greatest importance to the economy of Western Canada. It is the high quality of the protein constituent, gluten, which allows it to command a premium on the world market. Although gluten has been the object of a great deal of study, the chemistry of it is not well understood. In view of the important role of this protein material, more complete knowledge of its chemical and physical properties is desirable. The study of gluten can be regarded as a general, long term problem for research which may be approached in many different ways. Since glutamic acid comprises about forty percent of the gluten, a study of the properties of various compounds involving that amino acid in a number of ways should be useful in the final elucidation of the gluten structure. Previous work on this problem at the University of Saskatchewan has consisted of hydrolysis, dialysis and analytical work on wheat gluten (1, 2). Studies of polymers of glutamic acid have been done and later copolymers of glutamic acid, lysine and cysteine were studied in the belief that the latter polypeptides had properties resembling more closely those of natural proteins (3). The observation that pepsin and pancreatin, in a consecutive reaction, did not hydrolyse the polymer of L-glutamic acid or the polymer of L-cysteine but did hydrolyze the copolymers of glutamic acid, cysteine and lysine is of significance in relation to the present work. In view of these findings and the large amount of related work that is reported in the literature, it was thought that valuable information could be gained from the study of synthetic dipeptides. A worthwhile contribution to the knowledge of wheat protein structure may be obtained by comparing the action of well characterized proteases on wheat gluten and on synthetic substrates of known structure. This research was undertaken to obtain general basic information on the proteolytic constituents of some crude fungal enzyme preparations. A knowledge of these properties is necessary for studies involving fractionation of the crude material; for evaluating their usefulness in the study of gluten; and for assessing other possible uses for the enzymes. The problem involved the synthesis of some dipeptides and derivatives and a study of the conditions under which the enzymes could be made to hydrolyse these substrates. Although it was not the object in the first phase of the work to try to establish new methods of synthesis, an attempt was made to critically appraise those which were used. From the work with the enzymes it was hoped to determine in what respects the fungal enzymes differ from each other and from other proteolytic enzymes that have been studied in detail.