Converts the free carboxyl group of a malonyl-thioester to its methyl ester by transfer of a methyl group from S-adenosyl-L-methionine (SAM). It allows synthesis of pimeloyl-ACP via the fatty acid synthetic pathway (By similarity). Catalyzes a mechanistically unusual reaction, the ATP-dependent insertion of CO2 between the N7 and N8 nitrogen atoms of 7,8-diaminopelargonic acid (DAPA, also called 7,8-diammoniononanoate) to form a ureido ring. (7R,8S)-7,8-diammoniononanoate + ATP + CO2 = (4R,5S)-dethiobiotin + ADP + 3 H(+) + phosphate malonyl-[ACP] + S-adenosyl-L-methionine = malonyl-[ACP] methyl ester + S-adenosyl-L-homocysteine Cofactor biosynthesis; biotin biosynthesis; biotin from 7,8-diaminononanoate: step 1/2. Cofactor biosynthesis; biotin biosynthesis. In the N-terminal section; belongs to the methyltransferase superfamily. In the C-terminal section; belongs to the dethiobiotin synthetase family.