The vitamin B12 group. Presence of 2-methyl purines in factors <i>A</i> and <i>H</i> and isolation of new factors

Abstract

vitamin B12 ' titres obtained by Dulaney & Williams (1953).6.The biosynthesis of true vitamin B12 is com- petitively inhibited by phenylenediamine.7. The biosynthesis of the new material in the presence of phenylenediamine is competitively inhibited by 1:2-diamino-4:5-dimethylbenzene.The inhibition index lies somewhere between l60 and 320.The authors wish to express their thanks to Miss R. A. Brill and to Miss C. M. Lovejoy for valuable technical