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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.
There are various phosphate esters in living body including nucleic acid, and phosphorylation reaction related to their synthesis and interconversion is the basis of biochemical reaction. [2] [3] In most cases, ATP is the substrate of the phosphate group as a substrate and the enzyme that catalyzes these reactions is referred to as kinase. [4]
In biochemistry, a kinase (/ ˈ k aɪ n eɪ s, ˈ k ɪ n eɪ s,-eɪ z /) [2] is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule donates a phosphate group to the substrate molecule.
Phosphorylation allows cells to accumulate sugars because the phosphate group prevents the molecules from diffusing back across their transporter. 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:
A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions.
It was found that an enzyme, named phosphorylase kinase and Mg-ATP were required to phosphorylate glycogen phosphorylase by assisting in the transfer of the γ-phosphoryl group of ATP to a serine residue on phosphorylase b. Protein phosphatase 1 is able to catalyze the dephosphorylation of phosphorylated enzymes by removing the phosphate group.
Substrate-velocity relationships and induced transport tests have revealed that the dephosphorylated enzyme then facilitates the transfer of a phosphoryl group from the glucose-1,6-bisphosphate intermediate to the enzyme, regenerating phosphorylated phosphoglucomutase and yielding glucose 6-phosphate (in the forward direction).
This step is the enzymatic transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP by phosphoglycerate kinase, forming ATP and 3-phosphoglycerate. At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized.