3-Amino-4-hydroxybenzoic Acid Is Derived from the Tricarboxylic Acid Cycle Rather Than the Shikimic Acid Pathway1

The biosynthesis of 4-hydroxy-3-nitrosobenzamide in Streptomyces murayamaensis mutants MC2 and MC3 has been studied using sodium [1,2- 13 C 2 ]- and [1- 13 C, 18 O 2 ]acetate, sodium [2,3- 13 C 2 ]succinate, [1,2- 13 C 2 ]glutamic acid, [4- 13 C]aspartic acid, and sodium [1- 13 C]- and [2,3- 13 C 2 ]pyruvate. 13 C 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-carbon unit, possibly phosphoenol pyruvate. Subsequent specific incorporations of the labeled succinic acid, aspartic acid, and glutamic acid confirmed the TCA cycle involvement and the orientation of the four-carbon intermediate. Specific incorporation of the labeled pyruvic acids confirmed the involvement of a three-carbon unit and defined its orientation. This is the first aminohydroxybenzoic acid derivative shown not to be derived from a shikimic acid-type pathway, and its origin provides a rationale for the biosynthesis of other microbial products such as asukamycin, manumycin, and the michigazones.