In the first step of peptide synthesis this enzyme activates phenylalanine and racemizes it to the D-isomer. ATP + H2O + L-phenylalanine = AMP + D-phenylalanine + diphosphate + H(+) Binds 1 phosphopantetheine covalently. Antibiotic biosynthesis; gramicidin S biosynthesis. Large multienzyme complex of GrsA and GrsB. One-module-bearing peptide synthase with a C-terminal epimerization domain. Each module incorporates one amino acid into the peptide product and can be further subdivided into domains responsible for substrate adenylation, thiolation, condensation (not for the initiation module), and epimerization (optional), and N methylation (optional) (By similarity). The racemization reaction takes place in the thioester-bound stage of phenylalanine that is formed via the thiol group of the serine-bound phosphopantetheine. Belongs to the ATP-dependent AMP-binding enzyme family.