Purification and enzymological properties of the bacterial thiaminase I produced by B. thiaminolyticus Strain, B isolated from soil has been described.
By applying the culture filtrate of the bacteria to ammonium sulfate fractionation and chromatographic fractionation using a DEAE-Sephadex A-50, Sephadex G-100(1st), Hydroxyl apatite, and Sephadex G-100(2nd), an enzyme preparation having ca. 260 times as much specific activity as that of the original crude enzyme was obtained. The enzyme was homogeneous on polyacrylamide disc gel electrophoresis and had a molecular weight, estimated by gel filtration, of 37,000 daltons. The optimum pH and the optimum temperature were 5.0 and 50℃ respectively. The metal ions such as <Cu>^<2+>, <Ag>^+, and <Hg>^<2+>, and PCMB remarkably inhibited the activity of the enzyme.
The kinetic parameters for the base-exchange reaction of the enzyme were determined at pH 5.0 and 50℃. The Km values for thiamine and pyridine were 2.7 and 12.8mM, respectively, and the V_max value was 120mg/mg protein/mm, expressed as the amount of thiamine decomposed.
These properties were compared with those of thiaminases from B. thiaminolyticus Matsukawa et Misawa and Cl. sporogenes.