Cappiello M, Giuliani L, Pacifici G M
Department of General Pathology, Medical School, University of Pisa, Italy.
Pharmacology. 1990;40(2):69-76. doi: 10.1159/000138643.
Phenol and catechol sulphotransferases were studied with p-nitrophenol and dopamine as substrates in the mucosa of the ileum and colon obtained from 6 subjects and also in the liver from 6 subjects. The ileum and colon were from the same donor. The kinetics of phenol and catechol sulphotransferases were studied in each tissue specimen. The maximum velocity of reaction (Vmax) for phenol sulphotransferase (in pmol X min-1 X mg-1; mean +/- SD) was 165 +/- 28 (ileum), 79 +/- 42 (colon) and 1,361 +/- 370 (liver), whereas Vmax for catechol sulphotransferase was 489 +/- 75 (ileum), 198 +/- 93 (colon) and 39 +/- 23 (liver). Phenol sulphotransferase is the predominant pathway in the liver, whereas catechol sulphotransferase is the predominant pathway in the intestine. The ileum catalysed the sulphation of p-nitrophenol and dopamine at a higher rate than the colon. The Michaelis-Menten constant (Km) for phenol sulphotransferase (in mumol/l; mean +/- SD) was 0.96 +/- 0.11 (ileum), 1.00 +/- 0.19 (colon) and 0.84 +/- 0.07 (liver), whereas Km for catechol sulphotransferase was 17.8 +/- 2.8 (ileum), 18.2 +/- 3.4 (colon) and 21.4 +/- 1.2 (liver). Km values of hepatic phenol or catechol sulphotransferases are not different from those of intestinal enzymes. Previous work has shown that 2-naphthol sulphotransferase obeys non-Michaelis-Menten kinetics in the human intestinal mucosa [Pharmacology, 1988;43:411]. Here, we show that 2-naphthol is sulphated by at least two enzymes in human intestine.
