In enzymology, precorrin-6A synthase (deacetylating) () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are S-adenosyl methionine, precorrin 5, and H<sub>2</sub>O. Its 3 products are S-adenosylhomocysteine, precorrin 6A, and acetate.
This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:precorrin-5 C1-methyltransferase (deacetylating). Other names in common use include precorrin-6X synthase (deacetylating), and CobF. This enzyme is part of the biosynthetic pathway to cobalamin (vitamin B<sub>12</sub>) in aerobic bacteria.