Abstract
Among the thiamine derivatives tested, thiamine disulfide (TDS), O-benzoylthiamine disulfide and O, S-diacetylthiamine showed to be definitely inhibitory to urease activity. On the other hand, O, S-dibenzoylthiamine, O, S-dicarbethoxythiamine and thiamine had no inhibitory action. These inhibitions were observed at the alkaline pH and progressive with time, and could be prevented or recovered by the addition of an excess amount of sulfhydryl compounds. The reaction of TDS with crystalline urease produced thiamine bound urease with loss of its ureolytic activity, from which thiamine was liberated by sulfhydryl compounds. Therefore the mechanism of inhibition of urease activity by the disulfide compounds seems to be due to disulfide-exchange reactions between the S-S group of TDS and the SH groups of urease.
