EmbdenMeyerhofParnas

The Embden-Meyerhof-Parnas pathway, commonly called glycolysis, is the dominant cytosolic pathway for the breakdown of glucose in many organisms. It converts one molecule of glucose into two molecules of pyruvate, yielding ATP and NADH in the process. The pathway is named after Gustav Embden, Otto Meyerhof, and Jakub Parnas, who described its steps in the early 20th century.

In the cytosol, glycolysis consists of ten enzyme-catalyzed steps and proceeds through two phases: an energy-investment phase that consumes two ATP, and an energy payoff phase that yields four ATP and two NADH per glucose. Key steps include the phosphorylation of glucose to glucose-6-phosphate, isomerization to fructose-6-phosphate, and phosphorylation by phosphofructokinase-1 (a major regulatory point) to fructose-1,6-bisphosphate. This molecule is split into two triose phosphates, which are ultimately converted to pyruvate via glyceraldehyde-3-phosphate dehydrogenase, substrate-level phosphorylation by phosphoglycerate kinase and pyruvate kinase, and additional rearrangements.

Under aerobic conditions, pyruvate may be transported into mitochondria and oxidized further via the citric acid cycle and oxidative phosphorylation; under anaerobic conditions, it is reduced to lactate in animals or to ethanol and CO2 in yeasts and some plants. The EMP pathway provides ATP and reducing equivalents and supplies metabolic intermediates for biosynthesis, making it central to cellular energy production and metabolism.