The equivalence of thiamin and pyridoxine for a strain of Saccharomyces cerevisiae. II. The loss of pyridoxine during growth and the sparing effect of thiamin transaminase activity.

The observation that thiamin (B1) or pyridoxine (B.) serves as an alternate growth stimulant for one strain of brewers' top yeast and the conditions under which this equivalence occurs have been discussed elsewhere (Moses and Joslyn, 1953). The ability of the organism to synthesize thiamin or pyridoxine when grown in media deficient in either and its ability to form carboxylase under these conditions were demonstrated. Additional data on the nature of the equivalence of thiamin and pyridoxine are presented here. This includes observations on decrease in pyridoxine content during growth, effect of thiamin on this, and on transaminase activity of the yeast grown under such conditions.