Glycolysis and Gluconeogenesis

Abstract

Carbon metabolic pathways are called central metabolic pathways as these are the key pathways to generate energy and intermediates for the synthesis of biomolecules. The major carbon metabolic pathways are glycolysis/glycolytic pathway/Embden–Meyerhoff–Parnas pathway (EMP), pentose phosphate pathway (PPP) and Entner–Doudoroff (ED) pathway. Glycolysis and pentose phosphate pathway are ubiquitous in all domains of life. Glycolytic pathway is an anaerobic pathway and does not require oxygen essentially for conversion of glucose to pyruvate. However, glycolysis is categorized as aerobic or anaerobic depending upon the oxidation of NADH generated during glycolysis. If NAD⁺ is generated through oxidative phosphorylation, it is aerobic glycolysis, and if it is generated through fermentation during production of lactic acid/alcohol, it is called anaerobic glycolysis. Detailed pathway and its regulation by the enzymes phosphofructokinase and pyruvate kinase are discussed. Further, synthesis of glucose from non-carbohydrate sources such as pyruvate, lactate, acetate, fatty acids and amino acids as a part of gluconeogenetic pathway is described. Regulation and coordination between gluconeogenesis and glycolysis is  also  described in terms of key regulatory metabolites.