An L-tyrosine:2-oxoglutarate aminotransferase and atromentin synthetase greA catalyze consecutive steps to turn over L-tyrosine into atromentin, which represents the generic precursor molecule for the entire terphenylquinone and pulvinic acid family of pigments, which are widely distributed secondary metabolites in homobasidiomycetes. The first step catalyzed by the aminotransferase converts L-tyrosine in to 4-hydroxyphenylpyruvate (4-HPP). Adenylation of two 4-HPP monomers by the greA adenylation (A) domain, covalent tethering of the monomers as a thioester and oxoester onto the greA thiolation (T) and thioesterase (TE) domains, respectively, and symmetric C-C-bond formation between two monomers catalyzed by the greA TE domain leads to atromentin. Optimum pH is 7.5. Optimum temperature is 23 degrees Celsius. Secondary metabolite biosynthesis. Belongs to the ATP-dependent AMP-binding enzyme family.