A Carotenogenic Enzyme Aggregate in Phycomyces: Evidence from Quantitive Complementation

Abstract

Wild-type Phycomyces blakesleeanus accumulates β-carotene, while the mutant strain C2 is unable to synthesize carotenoids, and the mutant strain C9 accumulates lycopene. Heterokaryons containing a proportion, p, of C2 nuclei and (l — p) of C9 nuclei accumulate lycopene, γ-carotene, and β-carotene in the relative amounts (l — p), p(l — p), and p2, respectively, for different values of p.It is shown that these results are expected from the operation of a carotenogenic enzyme aggregate that works as an assembly line and contains two copies of a cyclase, which is defective in strain C9, as well as other enzymes.