Fatty acid synthetase catalyzes the formation of long-chain fatty acids from acetyl-CoA, malonyl-CoA and NADPH. This multifunctional protein has 7 catalytic activities as an acyl carrier protein. acetyl-CoA + 2n H(+) + n malonyl-CoA + 2n NADPH = a long-chain fatty acid + n CO2 + (n+1) CoA + 2n NADP(+) Homodimer which is arranged in a head to tail fashion (By similarity). Interacts with CEACAM1; this interaction is insulin and phosphorylation-dependent; reduces fatty-acid synthase activity (By similarity).