Acetate–Malonate Pathway: Fatty Acids and Polyketides

Abstract

The acetate–malonate pathway produces fatty acids and polyketides. Fatty acids, consisting of an aliphatic carbon chain with a carboxylic acid group at one end and a methyl group at the other end, are biosynthesized in the chloroplasts in the green tissues and in the plastids of non-photosynthetic tissues. Biosynthesis of fatty acid starts from acetyl-CoA. Two enzyme systems, namely acetyl-CoA carboxylase and fatty acid synthase are required for fatty acid biosynthesis. Lipoic acid is biosynthesized in mitochondria. Triacylglycerols, waxes, lipid polyesters (cutin, suberin), sphingolipids or oxylipins are then produced from the different saturated, unsaturated, and very long chain fatty acids. Different types of such lipids are components of membranes, cell walls, storage molecules, and signaling molecules. Polyketides are mostly aromatic derivatives and are differentiated by their methods of biogenesis. The enzymes that make the polyketide backbone are polyketide synthases of three types: type I, type II, and type III. Generally, polyketides are divided into two groups. These are (1) complex polyketides such as macrolides and (2) aromatic polyketides such as 6-methylsalicylic acid, usnic acid, aflatoxins, anthraquinones, flavonoids, stilbenes, curcuminoids, coniine related alkaloids etc.