Biosynthesis of 3-amino-4-hydroxybenzoic acid in Streptomyces murayamaensis: incorporation of [4-13C]oxalacetate

The biosynthesis of 3-amino-4-hydroxybenzoic acid (3,4-AHBA), a precursor to several Streptomyces secondary metabolites, requires the condensation of a three-carbon compound with a four-carbon unit derived from the tricarboxylic acid cycle. Using the ferrous chelate of 4-hydroxy-3-nitrosobenzamide, a metabolite of S. murayamaensis, as a model system, the exact nature of the four-carbon unit was explored. Incorporation experiments with [1-13C]methionine, [1-13C]homoserine, and [4-13C]oxalacetate revealed that only oxalacetate is a precursor to 3,4-AHBA.