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Pyruvate kinase is the enzyme involved in the last step of glycolysis.It catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP), yielding one molecule of pyruvate and one molecule of ATP. [1]
d -Glucose + 2 [NAD] + + 2 [ADP] + 2 [P] i 2 × Pyruvate 2 × + 2 [NADH] + 2 H + + 2 [ATP] + 2 H 2 O Glycolysis pathway overview The use of symbols in this equation makes it appear unbalanced with respect to oxygen atoms, hydrogen atoms, and charges. Atom balance is maintained by the two phosphate (P i) groups: Each exists in the form of a hydrogen phosphate anion, dissociating to contribute ...
The phosphoryl group on PEP is eventually transferred to the imported sugar via several proteins. The phosphoryl group is transferred to the Enzyme E I (EI), Histidine Protein (HPr, Heat-stable Protein) and Enzyme E II (EII) to a conserved histidine residue, whereas in the Enzyme E II B (EIIB) the phosphoryl group is usually transferred to a cysteine residue and rarely to a histidine.
Substrate-level phosphorylation exemplified with the conversion of ADP to ATP. Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP supported by the energy released from another high-energy bond that leads to phosphorylation of ADP or GDP to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level ...
In the case of glucose, the product of this phosphorylation is glucose-6-phosphate (Glc-6P). Due to the negative charge of the phosphate, this Glc-6P can no longer freely leave the cell. This is the first reaction of glycolysis , which degrades the sugar to pyruvate .
Thus, the two substrates of this enzyme are phosphoenolpyruvate and glycerone, whereas its two products are pyruvate and glycerone phosphate. This enzyme belongs to the family of transferases , specifically those transferring phosphorus-containing groups ( phosphotransferases ) with an alcohol group as acceptor.
Steps 1 and 3 require the input of energy derived from the hydrolysis of ATP to ADP and P i (inorganic phosphate), whereas steps 7 and 10 require the input of ADP, each yielding ATP. [7] The enzymes necessary to break down glucose are found in the cytoplasm, the viscous fluid that fills living cells, where the glycolytic reactions take place. [1]
Phosphorylation of glucose is a key reaction in sugar metabolism. The chemical equation for the conversion of D-glucose to D-glucose-6-phosphate in the first step of glycolysis is given by: D-glucose + ATP → D-glucose 6-phosphate + ADP ΔG° = −16.7 kJ/mol (° indicates measurement at standard condition)