Substrate specificity and some properties of phenol sulfotransferase from human intestinal Caco-2 cells.
The phase II metabolic reactions, sulfation and glucuronidation, were studied in a human colon carcinoma cell line (Caco-2), which has been developed as a model of intestinal enterocytes. Phenol sulfotransferase (PST, EC 2.4.2.1) was isolated from Caco-2 cells cultured for 7, 14 and 21 days. The enzyme catalyzed the sulfation of both p-nitrophenol and catecholamines (e.g., dopamine) as well as most catecholamine metabolites. The affinity (Km) of PST for dopamine was much higher than for p-nitrophenol, and the specific activity of PST with both substrates increased with the age of the cells. The thermal stability of Caco-2 PST increased with cell age and was not dependent on the acceptor substrate used. The thermolabile PST from 7-day old cells was more sensitive to NEM than was the thermostable enzyme from 21-day old cells. No UDP-glucuronyltransferase (EC 2.4.1.17) activity was detected in 7-, 14- and 21-day old Caco-2 cells with any of the methods used.
Baranczyk-Kuzma
A
A
Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66045.
Garren
J A
JA
Hidalgo
I J
IJ
Borchardt
R T
RT
D015239:Arylsulfotransferase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D003106:Colon / Q000201:enzymology; D004298:Dopamine / Q000378:metabolism; D004795:Enzyme Stability; D005033:Ethylmaleimide / Q000494:pharmacology; D014453:Glucuronosyltransferase / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology*; D007700:Kinetics; D009596:Nitrophenols / Q000378:metabolism; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured / Q000201:enzymology
D009596:Nitrophenols; D014453:Glucuronosyltransferase; D015239:Arylsulfotransferase; D005033:Ethylmaleimide; D004298:Dopamine; C024836:4-nitrophenol