Salinispora arenicola CNS-205 was a first-isolated obligate marine actinomycete. A gene (sare0357), annotated as ''amino acid adenylation domain'' located on the genome of Salinispora arenicola CNS-205, was cloned and characterized. The recombinant target protein Sare0357 was expressed in E. coli. Sare0357 specifically recognized and activated tryptophan (Trp) and phenylalanine (Phe). The basic kinetic parameters of Sare0357 for Trp were K (m) = 0.04 mM, V (max) = 2.1 mu M/min, k (cat) = 14.2 min(-1), and for Phe were K (m) = 0.03 mM, V (max) = 1.6 mu M/min, k(cat) = 10.4 min(-1). Our data elucidated Sare0357 biological role and biochemical properties as a Trp and Phe-activating adenylation domain.