Diazobenzenesulphonate selectively abolishes stimulation of glucuronidation by UDP-N-acetylglucosamine

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Abstract
Basal rates of glucuronidation of estrone (guinea pig) or of 4-nitrophenol (rat or guinea pig) were not significantly altered in sealed liver microsomal vesicles, treated with the membrane-impermeant protein-modifying agent diazobenzenesulfonate at 0.5-1.0 mM. Diazobenzenesulfonate abolished the normal stimulation of glucuronidation by UDP-N-acetylglucosamine. Ultrasonication to increase microsomal permeability activated glucuronidation by 680-750% and permitted significant inhibition by diazobenzenesulfonate. These findings are consistent with a model wherein glucuronyltransferases are embedded in the luminal leaflet of the endoplasmic reticulum and access of UDP-glucuronic acid to the transferases is facilitated by transmembrane carriers, which are stimulated by UDP-N-acetylglucosamine and are available to diazobenzenesulfonate; ultrasonication serves to permit access of diazobenzenesulfonate to glucuronyltransferases themselves, resulting in inhibition of their activity.

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