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Hydrolysis of stereoisomeric α-tocopheryl acetates catalyzed by bovine cholesterol esterase

From National Research Council Canada

DOIResolve DOI: https://doi.org/10.1016/0005-2760(87)90075-0
AuthorSearch for: 1; Search for: 1; Search for: 1; Search for: 1
Affiliation
  1. National Research Council of Canada
FormatText, Article
Subjectalpha tocopherol; alpha-tocopherol acetate; carboxylesterase; cholesterol esterase; cholic acid; cholic acid derivative; dimyristoylphosphatidylcholine; drug derivative; binding competition; catalysis; cattle; hydrolysis; kinetics; metabolism; protein binding; stereoisomerism; temperature; Binding, Competitive; Carboxylic Ester Hydrolases; Catalysis; Cattle; Cholesterol Esterase; Cholic Acid; Cholic Acids; Dimyristoylphosphatidylcholine; Hydrolysis; Kinetics; Protein Binding; Stereoisomerism; Support, Non-U.S. Gov't; Temperature; Vitamin E
Abstract
The kinetics of the bovine cholesterol esterase-catalyzed hydrolysis of three stereoisomers of α-tocopheryl acetate (αT-Ac) have been examined in vitro at 37°C in the presence of dimyristoylphosphatidylcholine and sodium cholate. In contrast to in vivo results obtained earlier in rats (Ingold, K.U., Burton, G.W., Foster, D.O., Hughes, L., Lindsay, D.A. and Webb, A. (1987) Lipids 22, 163-172), 2R,4'R,8'R-αT-Ac (RRR-αT-Ac) is hydrolyzed (to form "natural" vitamin E) more slowly (by a factor of approx. 7) than SRR-(and SSS-αT-Ac. It is concluded that chirality at position 2 plays the dominant role in determining Vmax . The Kn values show that RRR-αT-Ac is 2.1- and 2.7-times more strongly bound to the enzyme than are the SRR- and SSS-αT-Ac, respectively. The reaction is subject to competitive inhibition by the product with RRR-aT being 2.3-times as powerful an inhibitor as SRR--αT. © 1987.
Publication date
In
  • Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism 921, no. 3 (1987): 481–485.
LanguageEnglish
Peer reviewedYes
NPARC number21276604
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