SYNTHESIS OF UNSATURATED FATTY ACIDS BY PENICILLIUM CHRYSOGENUM

Actively growing mycelia of Penicillium chrysogenum produced linoleate and linolenatefrom 1-14C-labeled capric, lauric, and oleic acids (50% conversion), palmitic and stearic acids (20%), and slightly from myristic acid (5%,). Absence of substantial label in shorter chain products and location of label in oxidation products indicated that the polyunsaturated acids resulted from direct elongation and desaturation of the substrates. When acetate-1-14C was the substrate, the label was found in the 1-position of all unsaturated as well as saturated fatty acids in 1.5 min. Thereafter, label accumulation was mainly in the alkyl portions of the fatty acids. The data suggest that endogenous fatty acids were elongated to C18 with acetate and desaturated in a sequential pattern: stearate→oleate→linoleate→linolenate. Although myristic acid was not utilized well when added to the medium as substrate, the cellular myristate fraction had a high specific radioactivity when capric-1-14C and lauric-1-14C acids were substrates. Furthermore, the myristate fraction showed a transient high specific radioactivity after the addition of acetate-1-14C to an actively growing culture. Thus, myristate appears to function as an intermediate. Perhaps its failure as a substrate reflects an inferior capacity of myristic acid to form an enzyme-bound intermediate required of a precursor for elongation and desaturation. © 1969.