The metabolism of oxybiotin in yeast.

The demonstration of the marked biological activity of oxybiotin (l-4), the oxygen analogue of biotin, has focused attention upon the mode of action of this compound. It became of particular interest to determine whether oxybiotin possesses intrinsic activity or whether its biological potency is due to its conversion into biotin. The evidence in the literature is conflicting on this point. Hofmann and Winnick (5), employing a differential assay procedure based upon the selective destruction of biotin activity by dilute potassium permanganate, have demonstrated that Saccharomyces cerev&iae and Rhizobium trifolii utilize oxybiotin as such and do not convert it into biotin. On the other hand, Rubin et al. (6) have presented data from balance studies on S. cerevisiae, which indicates that 0-heterobiotin’ was converted into biotin or some other compound which possessed more activity for S. cerevisiae than did oxybiotin. The experiments described in this paper were designed to clarify this controversial point. The yeast balance studies of Rubin et al. (6) were repeated under conditions identical with those employed by these authors. In addition, three differential assay procedures for the determination of oxybiotin in the presence of biotin have been utilized to ascertain whether cells of Saccharomyces cerevisiae grown in the presence of oxybiotin contain biotin. These four independent experimental approaches led to the same conclusion; namely, that Saccharomyces cerevisiae does not convert, oxybiotin into biotin.