Biochemistry

The “ starting ” substance of fatty acid biosynthesis is malonyl-CoA. It is formed from acetyl-CoA by addition of activated carbonic oxide. 0 0 0 0 II H \\ // CHaCCHj-C +АТР+СО2+ЩО +blotlnenzyme C-CHj-C + orthophosphatetbiotinenzyme \ * Acetyl-CoA / \ SCoA carboxylase HO . SCoA Acetyl-CoA Malonyl-CoA Synthetase consists of seven enzymes that form a spherical particle, in the center of which is located acetyl-transfering protein (ATP). During the synthesis, source substrates are added to it - acetyl-CoA, malonyl- CoA, and it moves them from one enzyme to another. At the beginning of the synthesis, acetyl-CoA and malonyl-CoA arc added to synthetase with the participation of ATP and acetoacetyl-ATP is formed. Then it moves to the next enzyme {reductase}, which transfers it two hydrogen atoms from NADPH • H 2 . The resulting substance interacts with the enzymes that make up synthetase. This ends one cycle of synthesis, and the carbon chain of the acid is extended by two carbon atoms. Without splitting from ATP, the fatty acid is included in the next synthesis cycle, which begins with the addition of malonyl-CoA to it. This process is repeated until the fatty acid necessary for the cell is synthesized with a certain number of carbon atoms. The resulting acid is split from synthetase, enters into other reactions, and the initial substrates are added to synthetase, and the synthesis of the next saturated fatty acid molecule begins (Fig. 10.5). Unsaturated fatty acids are not synthesized in the human body, so they must be received with food. At the last stage of the synthesis of triacylglycerols, glycerophosphate interacts with two molecules of activated fatty acids. First, phosphatidic acid is formed, which is an intermediate product in the formation of triacylglycerols and phospholipids. 201