キノチアミンおよびL-システインエチルエステルを基質とする新チアミナーゼ活性測定法

A new method for the determination of transferase activity of thiaminase I and II was proposed. Thiaminase II which has been classified into a hydrolase showed transferase activity by the use of quinothiamine (Pm-quinoline) and L-cysteine ethylester as substrates.
Transferase activity of thiaminase I or II at 37℃ was able to be evaluated from the time course of absorbance (315 nm) for the reaction solution prepared by mixing 0.3 ml of 2 mM Pm-quinoline, 0.3 ml of 500 mM L-cysteine ethylester, 2.0 ml of 0.1 M Tris-HCl buffer (pH 8.8), and 0.4 ml of the enzyme solution. The Km values for Pm-quinoline and L-cysteine ethylester were determined to be 0.025 and 7.1 mM, respectively, in the case of thiaminase I and 0.094 and 0.9 mM, respectively, in the case of thiaminase II.