Catalyzes the methylation of C-1 in precorrin-5 and the subsequent extrusion of acetic acid from the resulting intermediate to form cobalt-precorrin-6A. H2O + precorrin-5 + S-adenosyl-L-methionine = acetate + 2 H(+) + precorrin-6A + S-adenosyl-L-homocysteine Cofactor biosynthesis; adenosylcobalamin biosynthesis; cob(II)yrinate a,c-diamide from precorrin-2 (aerobic route): step 5/10. Was originally thought to originate from Pseudomonas denitrificans, but similarity searches show that the sequence is much closer to Sinorhizobium. The entry's taxonomy has been changed.