Catalyzes the conjugation of specific amino acids (e.g. Glu and possibly His, Lys, and Met) to their preferred acyl substrates (e.g. 4-substituted benzoates), in a magnesium ion- and ATP-dependent manner. Can use 4-substituted benzoates such as 4-aminobenzoate (pABA), 4-fluorobenzoate and 4-hydroxybenzoate (4-HBA), and, to a lesser extent, benzoate, vanillate and trans-cinnamate, but not 2-substituted benzoates and salicylic acid (SA), as conjugating acyl substrates. Involved in both basal and induced resistance in a SA-dependent manner. Confers resistance to virulent and avirulent pathogens (at least bacteria and oomycetes), and promotes SA glucosides accumulation. Required for the establishment of hyper-sensitive response (HR) upon incompatible interaction and subsequent systemic acquired resistance (SAR). Specifically and reversibly inhibited by salicylic acid (SA). Optimum pH is 8-8.5. Interacts with the P.syringae pv. maculicola effector HopW1-1 (via C-terminus). Expressed in seedlings, mostly in cotyledons, leaves, hypocotyls and sporadically in roots. Not detected in unchallenged adult plants, except in flowers. Observed in young plants. In flowers, first detected in flower buds at the beginning of the floral stage 13. In petals, levels fade out during flower maturation do disappear at floral opening. Present in sepals and to some extent in stamen and carpel. By P.syringae pv. maculicola and pv. tomato. Induced by PAD4 locally at the infection site and in a salicylic acid-dependent manner systemically. Enhanced susceptibility to virulent and avirulent bacterial pathogens P.syringae pv. tomato and pv. maculicola ES4326 with or without DC3000(avrPphB, avrRpt2, avrB, avrRpm1, or avrRps4) as well as to the oomycete pathogen Hyaloperonospora parasitica (downy mildew) isolates Emoy2, Hind4, Hiks1, Wela3, Cand5, and Wand1. Impaired hyper-sensitive response (HR) and systemic acquired resistance (SAR). Compromised salicylic acid glucosides (SAG) accumulation. Resistance is partially rescued by SA treatment. Belongs to the IAA-amido conjugating enzyme family.