Abstract
Some properties of the purified thiaminase I from Clostridium sporogenes ATCC 8075 were investigated. It had a pH optimum of 8.0 and a temperature optimum of 30℃. The enzyme activity was completely destroyed by heating for 10 min at 70℃. The activity of the enzyme was accelerated by several sulfhydryl compounds including 2-mercaptoethanol, cysteine, sodium thioglycolate, dithiothreitol and GSH. SH-reagents such as p-chloromercuribenzoate, sodium monoiodoacetate, 5,5'-dithiobis (2-nitrobenzoic acid), and o-iodosobenzoic acid were potent inhibitors of the enzyme, and the inhibition by SH reagents could be dissolved with 2-mercaptoethanol. Zn^<+2>, Cu^<+2>, Cu^+, Hg^<+2>, Hg^+, Ag^+, Co^<+2>, Cd^<+2> or Pb^<+2> ion were inhibitory to the enzyme, and its activity was restrored with 2-mercaptoethanol from the inhibition. The enzyme activity was accelerated with Ca^<+2> and inhibited by EDTA. The acceleration by Ca^<+2> was repealed by equimolar EDTA. These results indicated that the SH groups in the enzyme and Ca^<+2> are very important factors for exhibiting the thiaminase activity. The K_m values of the bacterial thiaminase I at 30℃, pH 8.0 in the presence of 1μM dithiothreitol were 2.08×10^<-5>M for thiamine and 3.06×10^<-5>M for pyridoxine as a second substrate.
