Studies on: The Specific Activity and Inhibition of Urease; Trypsin and Chymotrypsin Catalyzed Hydrolysis of Simple Peptides; Isomeric Transitions of Radioactive Tellurium

Author: Harmon, Kent Midgley

Year: 1949

Degree: Dissertation (Ph.D.)

Advisor: Niemann, Carl G.

Committee Member: Unknown, Unknown

Option: Chemistry; Physics

Abstract

It has been observed that the specific activity of urease in solutions containing hydrogen sulfide, or cysteine, and expressed in terms of arbitrary. units of urease activity per unit weight of enzyme taken as protein nitrogen is dependent~ within limits, upon the apparent enzyme concentration. The Michaelis constants of several urease preparations have been determined at 25° and pH 7.0 under conditions minimizing the above noted phenomenon.

It has been observed that urease is competitively inhibited by phosphate, but not by maleate or glycine buffers. The effects of several substituted ureas upon the kinetics of the urease-catalyzed hydrolysis of urea have been compared.

It has been observed that although the trypsin-catalyzed hydrolysis of benzoyl-1-arginineamide is apparently first order with respect to substrate, the first order rate constant is dependent upon the initial substrate concentration. Similar results have been obtained in a study of the hydrolysis, by chymotrypsin, of N-acetyl-1-tyrosylglycineamide, and possible explanations for the two cases have been advanced. Inhibition of chymotrypsin by N-acetyl-d-tyrosyl-glycineamide has been observed.

Unsuccessful attempts have been made to obtain proof of a proposed mechanism for the chemical changes which accompany the isomeric transition of Te127-129. Further information regarding the nature of these changes has been obtained.

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