Improving polyketide and fatty acid synthesis by engineering of the yeast acetyl-CoA carboxylase

Polyketides and fatty acids are important in the production of pharmaceuticals, industrial chemicals, and biofuels. The synthesis of the malonyl-CoA building block, catalyzed by acetyl-CoA carboxylase (Acc1), is considered a limiting step to achieving high titers of polyketides and fatty acids in Saccharomyces cerevisiae. Acc1 is deactivated by AMP-activated serine/threonine protein kinase (Snf1) when glucose is depleted. To prevent this deactivation, the enzyme was aligned with the Rattus norvegicus (rat) Acc1 to identify a critical amino acid (Ser-1157) for phosphorylation and deactivation. Introduction of a S1157A mutation into Acc1 resulted in 9-fold higher specific activity following glucose depletion. The enzyme was tested in yeast engineered to produce the polyketide 6-methylsalisylic acid (6-MSA). Both 6-MSA and native fatty acid levels increased by 3-fold. Utilization of this modified Acc1 enzyme will also be beneficial for other products built from malonyl-CoA.