EMPglykolyysin

EMPglykolyysi, often referred to as the Entner-Doudoroff pathway, is a metabolic pathway that microorganisms use to break down glucose. Unlike glycolysis, which is the more common pathway for glucose metabolism, the Entner-Doudoroff pathway is primarily found in prokaryotes, including many bacteria and archaea. This pathway serves as an alternative route for glycolysis, producing pyruvate as its end product.

The Entner-Doudoroff pathway begins with the phosphorylation of glucose to glucose-6-phosphate. This is then oxidized to 6-phosphogluconolactone. This step is catalyzed by a glucose-6-phosphate dehydrogenase enzyme. 6-phosphogluconolactone is then hydrolyzed to 6-phosphogluconate. The key distinguishing step of the Entner-Doudoroff pathway occurs when 6-phosphogluconate is dehydrated to form 2-keto-3-deoxy-6-phosphogluconate (KDPG). This reaction is catalyzed by a KDPG aldolase. Finally, KDPG is cleaved into one molecule of pyruvate and one molecule of glyceraldehyde-3-phosphate. The glyceraldehyde-3-phosphate then enters the final stages of glycolysis to produce another molecule of pyruvate.

The net yield of ATP from the Entner-Doudoroff pathway is lower than that of glycolysis. For every molecule of glucose metabolized, the pathway yields only one molecule of ATP and one molecule of NADH. This contrasts with glycolysis, which yields a net of two ATP and two NADH molecules per glucose. Despite its lower ATP yield, the Entner-Doudoroff pathway is crucial for the survival and growth of many microorganisms in environments where alternative carbon sources are limited. It is particularly important in bacteria that lack the enzymes required for the standard glycolysis pathway.