Biochemistry of lipid and carbohydrate biosynthesis

Dr. Daniel Brown

Lipids and carbohydrates are two of the most essential classes of biomolecules, involved in a wide range of metabolic processes and biological functions. The biosynthesis of these molecules is tightly regulated and highly complex, involving a series of enzymatic reactions and intricate signaling pathways. Lipid biosynthesis begins with the conversion of acetyl-CoA, a key metabolite generated by the breakdown of glucose or fatty acids, into malonyl-CoA by the enzyme acetyl-CoA carboxylase (ACC). Malonyl-CoA serves as the substrate for the fatty acid synthase (FAS) complex, a multi-enzyme system responsible for the sequential condensation and reduction of acetyl-CoA and malonyl-CoA to produce saturated and unsaturated fatty acids. The final step in lipid biosynthesis involves the modification of these fatty acids into various classes of lipids, including phospholipids, triglycerides, and cholesterol. Carbohydrate biosynthesis, on the other hand, primarily involves the synthesis of glucose, the primary source of energy for many cells. Glucose biosynthesis, also known as gluconeogenesis, begins with the conversion of pyruvate, a key metabolite generated by glycolysis, into oxaloacetate by the enzyme pyruvate carboxylase. Oxaloacetate is then converted into phosphoenolpyruvate (PEP), which serves as the substrate for the enzymes involved in gluconeogenesis. The major regulatory steps in this pathway include the conversion of fructose-1,6-bisphosphate to fructose-6- phosphate by fructose-1,6-bisphosphatase, and the conversion of glucose-6-phosphate to glucose by glucose-6-phosphatase.