Involved in the biosynthesis of petrobactin, a catecholate siderophore that functions in both iron acquisition and virulence (PubMed:17189355, PubMed:17346033). Catalyzes the adenylation of 3,4-dihydroxybenzoate (3,4-DHBA) to the corresponding AMP ester, followed by the transfer of the activated unit to the phosphopantetheine thiol of the aryl-carrier protein AsbD (PubMed:17346033). 3,4-dihydroxybenzoate + ATP + holo-[aryl-carrier protein] = 3,4-dihydroxybenzoyl-[aryl-carrier protein] + AMP + diphosphate 3,4-dihydroxybenzoate + ATP + H(+) = 3,4-dihydroxybenzoyl-5'-AMP + diphosphate 3,4-dihydroxybenzoyl-5'-AMP + holo-[aryl-carrier protein] = 3,4-dihydroxybenzoyl-[aryl-carrier protein] + AMP + H(+) ATP-pyrophosphate exchange is inhibited in vitro by nonhydrolyzable acylsulfamate analogs that mimic the AsbC-bound intermediate 3,4-dihydroxybenzoyl-AMP. kcat is 7.1 min(-1) with 3,4-DHBA as substrate. kcat is 9.1 min(-1) with ATP as substrate. Siderophore biosynthesis; petrobactin biosynthesis. The deletion mutant cannot produce petrobactin on iron-depleted medium. In vitro analysis show that mutants grow to a very limited extent as vegetative cells in iron-depleted medium but are not able to outgrow from spores under the same culture conditions. Belongs to the ATP-dependent AMP-binding enzyme family.