GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

11. MAIN MECHANISMS OF METABOLISM AND ENERGY CONVERSION IN MICROORGANISMS

11.5. PATHWAYS OF GLUCOSE AND OTHER CARBOHYDRATE CATABOLISM

11.5.1. Fructose-1,6-bisphosphate pathway (glycolysis)

The third name for this glucose catabolic pathway is the Embden–Meyerhof–Parnas pathway, named after the researchers who studied the process. It was first discovered in Muscle Tissues. Glycolysis Functions in animals, plants, and many microorganisms. During glycolysis, glucose is converted into Pyruvate (Fig. 11.3).

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Fig. 11.3. Glucose Catabolism. The Embden–Meyerhof–Parnas pathway

The processes converting glucose into glyceraldehyde-3-phosphate require energy input. During the subsequent oxidation of glyceraldehyde-3-phosphate to pyruvate, energy is released. The conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate is coupled with the phosphorylation of ADP to form ATP (catalyzed by phosphoglycerate kinase). This reaction is one of the key points in glycolysis where ATP is generated via substrate-level phosphorylation. Phosphoenolpyruvate (PEP) is the second compound containing a high-energy phosphate bond: during The formation of pyruvate from PEP, the phosphate group is transferred to ADP to yield ATP (catalyzed by pyruvate kinase). This reaction represents the second site of substrate-level ATP generation in the Embden–Meyerhof–Parnas pathway. Both energy-yielding reactions (ATP-generating steps) in the conversion of glyceraldehyde-3-phosphate to pyruvate serve as the primary energy-supplying stages for anaerobic microorganisms. Under anaerobic conditions, all carbohydrate-fermenting microorganisms rely on the energy derived from The oxidation of glyceraldehyde-3-phosphate to pyruvate.

All reactions of glycolysis, with the exception of three (hexokinase, Phosphofructokinase, and pyruvate kinase reactions), are fully reversible.

The overall reaction for Glucose breakdown via the Embden–Meyerhof–Parnas pathway can be represented as follows: