Inactivation of jack bean urease by allicin.

Allicin--diallyl thiosulfinate--is the main biologically active component of freshly crushed garlic. Allicin was synthesized as described elsewhere and was tested for its inhibitory ability against jack bean urease in 20 mM phosphate buffer, pH 7.0 at 22 degrees C. The results indicate that allicin is an enzymatic inactivator. The loss of urease activity was irreversible, time- and concentration dependent and the kinetics of the inactivation was biphasic; each phase, obeyed pseudo-first-order kinetics. The rate constants for inactivation were measured for the fast and slow phases and for several concentrations of allicin. Thiol reagents, and competitive inhibitor (boric acid) protected the enzyme from loss of enzymatic activity. The studies demonstrate that urease inactivation results from the reaction between allicin and the SH-group, situated in the urease active site (Cys592).