Studies in carotenogenesis. 26. The incorporation of [14C]acetate, [14C]mevalonate and 14CO2 into β-carotene by the fungus Phycomyces blakesleeanus

Abstract

The incorporation of [2-14]acetate into [beta]-carotene by P. blakesleeanus is decreased by DL-mevalonate and by L-leucine. DL-[2-14C]Mevalonate is incorporated into [beta]-carotene by P. blakesleeanus some 15 times more efficiently than [2-14C] acetate. The C-2 of mevalonate retains its individuality when incorporated into [beta]-carotene and occurs only in C-w of the isoprenoid residue. P. blakesleeanus cultured on our basal medium, with asparagine as the N source, does not fix CO2 into [beta]-carotene; however, when leucine is present in the medium 14CO2 appears in the [beta]-carotene. An explanation of this observation is offered. Labelled [beta]-carotene is synthesized by washed suspensions of P. blakesleeanus grown in the presence of diphenylamine and DL-[2- 14C]mevalonate.