STUDIES ON DEOXYTHIAMINE : (VI) THE INHIBITION EFFECT OF DEOXYTHIAMINE ON THIAMINE UPTAKE BY LACTIC ACID BACTERIA

Abstract

A new type of antithiamine compound, deoxythiamine(DOB_1), inhibits the growth of thiamine requiring microorganisms, such as Lactobacillus fermenti 36 or Kloeckera apiculata and competitively antagonizes thiamine (B_1) (Vitamins 22,200 ; 23,213,1961). In order to clarify the mechanism of action of this compound, the influence of DOB_1 on B_1 uptake by L. fermenti was observed using labeled B_1-^<35>S-HCl. Cells absorbed 73〜92% of B_1 under our experimental conditions. When DOB_1 was added to the incubation medium, the amount of absorbed B_1 decreased proportionally with the increase of DOB_1. The ratio of DOB_1 to B_1 to yield 50% of inhibition was 6 : l. Competitive inhibition was observed between DOB_1 and B_1. A comparison of the antagonistic activity by DOB_1 with several other antithiamine compounds was done and the order of their inhibition indices was as follows : pyrithiamine (2)>DOB_1 ≒ deoxymethylthiamine ≒ imidazolethiamine (6)> amprolium ≒ thiamine sulfuric acid ester (30). It was interesting to observe that the degree of inhibition of B_1 uptake by the antithiamine compounds was similar to their effects on cell growth.