Biosynthesis of retinoyl-beta-glucuronide, a biologically active metabolite of all-trans-retinoic acid.
All-trans-retinoic acid is metabolized in vitro to a biologically active metabolite, retinoyl-beta-glucuronide. We have studied the synthesis of this metabolite in vitro. The identity of the product was established by cochromatography on reverse-phase high-performance liquid chromatography, beta-D-glucuronidase hydrolysis, and fast atom bombardment and collisionally activated decomposition/fast atom bombardment mass spectrometry. The formation of retinoyl-beta-glucuronide is catalyzed by a UDP-glucuronosyltransferase with apparent Km's of 54.7 microM for all-trans-retinoic acid and 2.4 mM for UDP-glucuronic acid. The reaction requires enzyme, UDP-glucuronate, and no other factor. It is strongly inhibited by millimolar concentrations of coenzyme A. The specific activity of UDP-glucuronosyltransferase is greatest in the liver and least in the kidney of those tissues examined. The specific activity of the enzyme is increased by vitamin A deficiency. The increased specific activity observed in the vitamin A-deficient rat liver is uncharacteristic of retinoic acid inactivation enzymes; therefore, retinoyl-beta-glucuronide may be of functional importance.
Miller
D A
DA
DeLuca
H F
HF
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003067:Coenzymes / Q000378:metabolism; D005260:Female; D014453:Glucuronosyltransferase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D013696:Temperature; D014212:Tretinoin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism*; D014802:Vitamin A Deficiency / Q000201:enzymology
D003067:Coenzymes; C026787:retinoyl glucuronide; D014212:Tretinoin; D014453:Glucuronosyltransferase