【摘要】 <正> 緒言 Westenbrink等在研究維生素B₁對於酵母羧酶的激活作用時,間接地推测到此激活作用是磷酸酯酶被抑制,而保存了羧酶輔酶的結果。略後他們又直接地證明維生素B₁對於酵母的磷酸酯酶有強烈的抑制作用。幾乎同時Tuba在研究培養基的成份對於酵母磷酸酯酶的生成之影響,也發現維生素B₁有極強的更多还原

【Abstract】 Inhibition by thiamin of yeast "acid" phosphatase was noticeable at a concentration of 3×10^-5 M, and reached a maximum at 3×10^-4 M. On further increasing the concentration of thiamin, there was no corresponding increase in the extent of inhibition. Maximum inhibition was attained at different levels of residual activity, depending upon the substrate used. With β-glycerophosphate as substrate, maximum inhibition of over 50％ was obtained, while with phenyl phosphate, it was only about 30％. Thiarnin was also found to shift the optimum pH of the enzyme. With 0.005 M phenyl phosphate as substrate, the optimum pH dropped from 3.40. to 3.25. Inhibition was observed only on the alkaline side of the shifted optimum, being practically nonexistent on the acid side. Thiarnin. inhibition. was demonstrated to be completely reversible by dialysis against distilled water. From a study of the chemical kinetics of the enzyme it was concluded that the inhibition, by thiamin was essentially non-competitive in nature. 2-Methyl-5-cyano-6-amino-pyrimidine, a compound similar in structure to the pyrimidine moiety of the thiamin molecule, was also found to be an inhibitor of yeast "acid" phosphatase. Maximum inhibition also occurred at 3×10^-4 M, but the extent of inhibition at the maximum was much less, being only 14％ when phenyl phosphate was the substrate.更多还原