3-AMINO-4-HYDROXYBENZOIC ACID IS DERIVED FROM THE TRICARBOXYLIC-ACID CYCLE RATHER THAN THE SHIKIMIC ACID PATHWAY

The biosynthesis of 4-hydroxy-3-nitrosobenzamide in Streptomyces muray amaensis mutants MC2 and MC3 has been studied using sodium [1,2-C-13(2 )]- and [1-C-13,O-18(2)]acetate, sodium [2,3-C-13(2)]succinate, [1,2-C -13(2)]glutamic acid, [4-C-13]aspartic acid, and sodium [1-C-13]- and [2,3-C-13(2)]pyruvate. C-13 NMR analysis of the labeling patterns from the first two of these suggested a pathway via condensation of a four -carbon unit from the tricarboxylic acid (TCA) cycle with a three-carb on unit, possibly phosphoenol pyruvate. Subsequent specific incorporat ions of the labeled succinic acid, aspartic acid, and glutamic acid co nfirmed the TCA cycle involvement and the orientation of the four-carb on intermediate. Specific incorporation of the labeled pyruvic acids c onfirmed the involvement of a three-carbon unit and defined its orient ation. This is the first aminohydroxybenzoic acid derivative shown not to be derived from a shikimic acid-type pathway, and its origin provi des a rationale for the biosynthesis of other microbial products such as asukamycin, manumycin, and the michigazones.