Members of the 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthetase family catalyse the first step in aromatic amino acid biosynthesis from chorismate. Class I includes bacterial and yeast enzymes; class II includes higher plants and various microorganisms (see INTERPRO: IPR002480) [PMID:8760910].

The first step in the common pathway leading to the biosynthesis of aromatic compounds is the stereospecific condensation of phosphoenolpyruvate (PEP) and D-erythrose-4-phosphate (E4P) giving rise to 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP). This reaction is catalyzed by DAHP synthase, a metal-activated enzyme, which in microorganisms is the target for negative-feedback regulation by pathway intermediates or by end products. In Escherichia coli there are three DAHP synthetase isoforms, each specifically inhibited by one of the three aromatic amino acids. The crystal structure of the phenylalanine-regulated form of DAHP synthetase shows the fold as is a (beta/alpha) 8 barrel with several additional beta strands and alpha helices [PMID:10425687].