An enzyme complex for the dehydrogenation of phytoene in Phycomyces.

Phycomyces strain C5, carrying mutation carB10, accumulates phytoene instead of beta-carotene. Heterokaryons containing C5 nuclei and different other nuclei carrying the wild type carB allele accumulate significant amounts of phytofluene, zota-carotene and neurosporene. From quantitative analyses of carotenes and nuclear proportions in the heterokaryons we conclude that four copies of the carB gene product, assembled in an enzyme complex, act sequentially in the conversion of phytoene to lycopene.