Inactivation of rhodanese from human gastric mucosa and stomach adenocarcinoma by 2,4, 6-trinitrobenzenesulphonate and by 4,4'-diisothiocyanatostilbene-2,2'-disulphonate.

Rhodanese (thiosulphate sulphurtransferase, EC 2.8.1.1) was partially purified from normal human gastric mucosa and from gastric adenocarcinoma by DEAE-cellulose column chromatography. Rhodanese inactivation by 2, 4, 6-trinitrobenzenesulphonate and by 4,4'-diisothiocynatostilbene-2-2'-disulphonate was studied by an analysis of the time-dependence of rhodanese activity loss. Rhodanese inactivation by 2, 4, 6-trinitrobenzenesulphonate was, under all conditions tested, found to be first-order with regard to enzyme residual activity. In contrast to this, rhodanese inactivation by 4, 4'-diisothiocyanatostilbene-2, 2'-disulphonate was found to be biphasic, when log residual enzyme activity was plotted vs reaction time. The first-order rate constant, k, for rhodanese inactivation by 2, 4, 6-trinitrobenzenesulphonate was, at all pH values tested, higher with the gastric adenocarcinoma enzyme than with the normal mucosa enzyme: at pH 8.00, k is 27.0 per hour, for the normal mucosa enzyme, while for the adenocarcinoma enzyme k is 69.0 per hour. In contrast to this, no difference in the inactivation profile of the normal mucosa enzyme and the gastric adenocarcinoma enzyme was to be observed with 4,4'-diisothiocyanatostilbene-2,2'-disulphonate.