Catalyzes the conversion of a double bond to a cyclopropane ring at the distal position of an alpha mycolic acid via the transfer of a methylene group from S-adenosyl-L-methionine. 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 Lipid metabolism; mycolic acid biosynthesis. Homodimer. Belongs to the CFA/CMAS family.