Mechanism of Photoregulated Carotenogenesis in Rhodotorula minuta VIII. Effect of Mevinolin on Photoinduced Carotenogenesis

Mevinolin, which is a highly specific competitive inhibitorof 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase,was used in a search for photoinducible enzyme(s) other thanHMG-CoA reductase in the pathway of carotenoid biosynthesisin Rhodotorula minuta. The photoinduced production of carotenoids was competitivelyinhibited by mevinolin. The concentration of mevinolin thatis required to inhibit completely the production of carotenoidsdepends on the light dose given to the cells. However, the relationshipbetween the inhibition ratio and the concentration of mevinolinwas almost identical regardless of the light dose. These resultssuggest that the activity of enzymes involved in the formationof HMG-CoA may not be affected by light. When an adequate amount of mevalonate was added to the growthmedium that contained sufficient mevinolin for the completeinhibition of the photoinduction of the production of carotenoids,the same quantity of carotenoids was produced as in the absenceof mevinolin. Moreover, the production of carotenoids in thepresence of both mevinolin and mevalonate was inhibited by cycloheximide. It appears from these results that one or more photoinducibleenzymes, such as HMG-CoA reductase, may be present in the carotenogenicpathway beyond mevalonate. (Received April 12, 1989; Accepted January 16, 1990)