Involvement of AfsA in A-factor Biosynthesis as a Key Enzyme.

The afsA gene of Streptomyces griseus has been postulated to encode a key enzyme for A-factor biosynthesis from primary metabolites commonly present in Streptomyces strains. Escherichia coli cells harboring afsA under the control of the T7 promoter specified distinct A-factor activity in the culture broth, as determined by induction of streptomycin production and aerial mycelium and spore formation in an A-factor-deficient S. griseus mutant strain. Production of the substance(s) having A-factor activity was inhibited by cerulenin, an inhibitor of fatty acid biosynthesis. These observations suggest that afsA encodes a key enzyme in the A-factor biosynthetic pathway in which a beta-keto acid derived from fatty acid biosynthesis and a glycerol derivative serve as precursors.