Beef liver esterase. II. Kinetic properties |
| |
Authors: | D Wynne S Ginsburg Y Shalitin |
| |
Institution: | Department of Biology, Technion—Israel Institute of Technology, Haifa, Israel |
| |
Abstract: | The kinetic parameters, kcat and KM, in beef liver esterase-catalyzed hydrolysis were determined for about 100 substrates, which can be classified in several groups: (1) In the ethyl ester series of fatty acids KM decreases with elongation of the acid, while kcat has a maximum value with pentanoate. (2) Alkyl acetates are better substrates as the alkyl moiety is longer, whereas esters with branched alkyl groups become worse substrates. (3) Aryl esters are very good substrates. (4) Esters of dicarboxylic acids are good substrates, but only one ester group is cleaved by the enzyme. Fumarate diester is susceptible to esterase hydrolysis, while maleate is not. (5) Esters of hydrophobic amino acids are very good substrates; the enzyme is not stereoselective and both the l and d stereoisomers are readily hydrolyzed. Branching at the β-carbon atom leads to loss of activity, and blocking of the amino group abolishes it. Fluoride ion and dl-malate esters are potent competitive inhibitors of the enzymic reaction. The optimal pH was found to lie between 8 and 8.5. The reaction rate increased between 5 and 40 °C then dropped sharply. The activity decreased at high salt concentration. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|