Die Regulation der Synthese der Riboflavinsynthetase durch Eisen in flavinogenen Hefen

Abstract

Summary The influence of iron on the synthesis of riboflavin (RF) and riboflavin synthetase (RFS) activity in the cells of some flavinogenic and non-flavinogenic yeasts was investigated. It is shown that during the cultivation of Pichia guilliermondii, Torulopsis candida and Schwanniomyces occidentalis in iron-deficient media the induction of RF oversynthesis is correlated with an increase in the RFS activity. This phenomenon did not occur in iron-deficient cultures of weak RF producers such as P. ohmeri, Candida utilis and C. pulcherrima. The incubation of iron-rich cells of T. candida with α,α′-bipyridine or o-phenanthroline chelaters which possess a high affinity to iron also causes a marked increase of RFS activity and the flavino-genesis rate. Cycloheximide in low concentration abolishes this effect; the same does amino-acid starvation of the cells of the methionine-deficient mutant of T. candida, MET-2. The addition of Fe (II) ions to the suspension of young iron-deficient cells prevents the increase of RFS activity. The Fe (II) ions and the autolysates of iron-rich cells do not inhibit the RFS activity in crude extracts of iron-deficient cells of this species. It is concluded that iron participates in the regulation of RFS synthesis in the cells of flavinogenic yeasts.