Involved in the phagosome maturation block (PMB). Catalyzes the conversion of a double bond to a cyclopropane ring at the proximal position of an alpha mycolic acid via the transfer of a methylene group from S-adenosyl-L-methionine. It can use cis, cis 11,14-eicosadienoic acid and linoelaidic acid as substrate. Cyclopropanated mycolic acids are key factors participating in cell envelope permeability, host immunomodulation and persistence. 1-acyl-2-(9Z)-enoyl-sn-glycero-3-phospholipid + S-adenosyl-L-methionine = 1-acyl-2-(9-cyclopronane)-acyl-sn-glycero-3-phospholipid + H(+) + S-adenosyl-L-homocysteine Regulated by PknF. Inhibited by S-adenosyl-N-decyl-aminoethyl (SADAE), thiacetazone (TAC) and dioctylamine. Lipid metabolism; mycolic acid biosynthesis. Homodimer. Phosphorylation by PknF at Thr-168 and Thr-183 regulates the mycolic acid profile which affects colonial cording, intramacrophage replication and abrogates the PMB. Inactivation of pcaA does not affect initial growth of the organism over the first 3 weeks, but after 6 weeks, when wild-type organisms persist at a constant level indefinitely, the pcaA mutant is progressively eliminated from the animal. Cells lacking this gene accumulates a hybrid mycolate with a cis double bond at the proximal position in place of the cis cyclopropane present in wild-type alpha mycolate. Was identified as a high-confidence drug target. Belongs to the CFA/CMAS family.