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The kinase enzymes increase the rate of the reactions by making the inositol hydroxyl group more nucleophilic, often using the side chain of an amino acid residue to act as a general base and deprotonate the hydroxyl, as seen in the mechanism below. [24] Here, a reaction between adenosine triphosphate (ATP) and
Choline acetyltransferase (also known as ChAT or CAT) is an important enzyme which produces the neurotransmitter acetylcholine. [85] Acetylcholine is involved in many neuropsychic functions such as memory, attention, sleep and arousal. [86] [87] [88] The enzyme is globular in shape and consists of a single amino acid chain. [89]
The first step of this reaction is phosphorylation of the substrate via phosphotransferase during transport. 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.
Adenylate kinase (EC 2.7.4.3) (also known as ADK or myokinase) is a phosphotransferase enzyme that catalyzes the interconversion of the various adenosine phosphates (ATP, ADP, and AMP). By constantly monitoring phosphate nucleotide levels inside the cell, ADK plays an important role in cellular energy homeostasis .
Most glycosyltransferase enzymes form one of two folds: GT-A or GT-B. Glycosyltransferases (GTFs, Gtfs) are enzymes that establish natural glycosidic linkages.They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glycosyl acceptor molecule, the nucleophile of which can be oxygen- carbon-, nitrogen-, or sulfur ...
Above is a ball-and-stick model of the inorganic phosphate molecule (H PO 4 2−).Colour coding: P (orange); O (red); H (white). The chemical activity of a protein kinase involves removing a phosphate group from ATP and covalently attaching it to one of three amino acids that have a free hydroxyl group.
The protein kinase domain is a structurally conserved protein domain containing the catalytic function of protein kinases. [2] [3] [4] Protein kinases are a group of enzymes that move a phosphate group onto proteins, in a process called phosphorylation. This functions as an on/off switch for many cellular processes, including metabolism ...
It is known that in the absence of magnesium, no enzyme activity occurs. [9] The bivalent metal assists the enzyme ligands in shielding the bound phosphate group's negative charges, allowing the nucleophilic attack to occur; this charge-stabilization is a typical characteristic of phosphotransfer reaction. [10]