Designing Fluorescent Estrogen Mimetic 7-hydroxycoumarin Probe Substrates for Human Sulfotransferase Enzymes 

ABSTRACT

Sulfonation is one of drug metabolism reactions affecting homeostasis of estrogens. C-3 aryl substituted 7-hydroxycoumarins are fluorescent estrogen mimetics; i.e., the hydroxyl groups of both estrogens and 7-hydroxycoumarins are conjugated by human sulfotransferases (SULTs). Sulfonation of the 7-hydroxyl group by SULTs decreases the fluorescence of 7-hydroxycoumarins. Sulfonation of a series of 7-hydroxycoumarins by human SULTs was determined based on this property. SULT subtype-specific binding interactions of 7-hydrocoumarins were assessed against the modelled optimal arrangement needed for sulfonation. 3-(4-Methoxyphenyl)-7-hydroxycoumarin (11) and 3-(4-hydroxyphenyl)-7-hydroxycoumarin (9) were selective substrates for SULT1E1, whereas 3-(1H-1,2,4-triazol-1-yl)-7-hydroxycoumarin (14) was a selective SULT1A1 substrate. Other tested 7-hydroxycoumarin were sulfonated by more than two SULTs. Sulfonation of most 7-hydroxycoumarins by SULT1A1 or SULT1C4 followed Michaelis-Menten kinetics, while substrate inhibition kinetics occurred in sulfonation of several derivatives by SULT1E1. Selective sulfonation of derivatives 9 and 11 by SULT1E1 was due to the enzyme’s long and cylindrical active site that assures optimal 7-hydroxyl group placement in the precursory reaction state. SULT1A1 and SULT1C4 preferred smaller derivatives as substrates than the SULT1E. Estrogens potently inhibited the sulfonation of 3,4-dimethyl-7-hydroxycoumarin (4) by SULT1E1 (IC50 below 1 µM). SULT1A1 and SULT1C4 were less potently inhibited by the estrogens. Several 7-hydroxycoumarin derivatives share common binding interaction patterns with the estrogens at SULT1E1 and SULT1A1 active sites. Fluorescent 7-hydroxycoumarins could serve as convenient probe substrates for SULTs to evaluate their inhibition by new chemical entities during drug development. 7-Hydroxycoumarins 9 or 11 could be used as selective probe substrates for SULT1E1 and 14 for SULT1A1.

PMID:40885279 | DOI:10.1016/j.ejps.2025.107249