Influence of para substituent of phenol on phospholipid dependence of uridine diphosphate-glucuronyltransferase.
The influence of para substituent of phenol on the property of phospholipid dependence of uridine diphosphate-glucuronyltransferase (UDPGT) was studied using hepatic microsomes of the rats. para Substituents used were p-ethyl, p-tert-butyl and p-phenyl. Glucuronidations of phenol and its derivatives were inhibited with each other. When phospholipids of the microsomes were removed with phospholipase A2, Vmax and Km decreased in the order phenol, p-ethylphenol, p-tert-butylphenol, p-phenylphenol, indicating that this change by delipidation increased with van der Waals volume (Vw) of para substituent. Arrhenius plots of glucuronidation for phenol and p-ethylphenol exhibited a change in slope, responding to thermotropic property of the membrane labelled with 1,6-diphenyl-1,3,5-hexatriene (DPH). In contrast, p-tert-butyl and p-phenyl substituents showed linear Arrhenius plots. The activation energy (Ea) for glucuronidation of p-phenylphenol was increased by delipidation, whereas Ea of other substrates did not show any remarkable change.
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Tokai Research Laboratories, Daiichi Pure Chemicals Co., Ltd., Ibaraki, Japan.
D000818:Animals; D001711:Biotransformation; D002855:Chromatography, Thin Layer; D004734:Energy Metabolism; D005965:Glucuronates / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010636:Phenols / Q000737:chemistry / Q000494:pharmacology*; D010743:Phospholipids / Q000493:pharmacokinetics* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
D005965:Glucuronates; D010636:Phenols; D010743:Phospholipids; D014453:Glucuronosyltransferase