Possesses carboxylesterase activity in vitro with a preference for short acyl chain substrates. Functions as a negative regulator of the hypersensitive response (HR) triggered by the bacterial type III effector protein AvrBsT (PubMed:17293566). Possesses phospholipase A2 (PLA2) activity and hydrolyzes phosphatidylcholine (PC), a lipid that is hydrolyzed by phospholipase D (PLD) to produce phosphatidic acid (PA). Required to suppress AvrBsT-dependent HR and PLD-dependent production of PA in response to AvrBsT elicitation (PubMed:19918071). No visible phenotype under normal growth conditions, but mutant plants show hypersensitive response to infection with the bacterial pathogen Xanthomonas campestris pv. vesicatoria containing the type III effector protein AvrBsT. Belongs to the AB hydrolase superfamily. AB hydrolase 2 family.