Studies in carotenogenesis. 7. Further observations concerning the action of diphenylamine in inhibiting the synthesis of β-carotene in Phycomyces blakesleeanus

Abstract

The rate of production of the more saturated polyenes (phytofluene, etc.) is much more rapid in Phycomyces than is that of beta-carotene. The former have reached their max. values within 3-4 days of inoculation, while the latter is maximal only 5-7 days after inoculation. The decreased synthesis of beta-carotene and the increased synthesis of the phytofluene group which occurs in the presence of diphenylamine is directly proportional to the concn. of the inhibitor. No compound of similar structure or oxidation-reduction potential has been found which has the same effect on carotenogenesis as diphenylamine. Phenol is inactive. 2-Naphthylamine stimulates beta-carotene synthesis. FeSO4 does not counteract the action of diphenylamine. Either AMP (muscle adenylic acid) or riboflavin returns the synthesis of beta-carotene to normal in diphenylamine cultures, but neither lowers the synthesis of the more reduced polyenes to normal. Yeast adenylic acid is without effect. AMP alone has no effect on the growth, lipid production or carotene production by Phvcomyces. In growing cultures riboflavin, up to a concn. of 1/20,000, stimulates growth, lipogenesis and carotenogenesis, but lipogenesis is stimulated at all concns. of riboflavin tested. Mats cultured in the presence of diphenylamine and containing large amts. of the phytofluene group do not convert these into beta-carotene, when washed and transferred to non-diphenylamine media.