Abstract
(1) A thiamin kinase defective mutant of Escherichia coli W (70-23-102) accumulated free thiamin in the presence of glucose. The overshoot phenomenon of thiamin was not observed. This mutant cell accumulated nearly the same amount of thiamin diphosphate as the kinase positive cell, while the maximum accumulation of free thiamin was ca. 1/4. (2) Characteristics of uptake reaction were featured by those values like K_m of 0.8 nM, optimum pH of 6.8, optimum temperature of 45℃, and V_<in> of 31 nmol/g/min. (3) Thiamin-exit reaction of this mutant showed nearly complete NaN_3-inhibition, dependency on cellular thiamin (FIG. 8), optimum pH of 8.0, optimum temperature of 34℃, and V_<out> of 14 nmol/g/min.
