INTERACTION BETWEEN CERULENIN AND 6-HYDROXYMELLEIN SYNTHASE IN CARROTCELL-EXTRACTS

Activity of 6-hydroxymellein synthase, an induced polyketide synthetic enzyme in carrot cell extract, was not inhibited by cerulenin which i s known as a potent inhibitor for fatty acid synthases and biosyntheti c enzymes of various polyketide compounds. However, when 6-hydroxymell ein synthase was incubated with [H-3]cerulenin in the absence of its s ubstrates, acyl-CoAs, significant radioactivity was found to co-migrat e with the enzyme protein in SDS-PAGE analysis. The radioactivity asso ciated with the synthase was not observed when the cerulenin-enzyme co mplex was post-incubated with acyl-CoAs. These results suggest that ce rulenin is able to bind to 6-hydroxymellein synthase and forms a compl ex. However, the attachment is unstable and the substrates of the synt hase are capable of replacing the inhibitor at the reaction centre.