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Histidine (symbol His or H) [2] is an essential amino acid that is used in the biosynthesis of proteins.It contains an α-amino group (which is in the protonated –NH 3 + form under biological conditions), a carboxylic acid group (which is in the deprotonated –COO − form under biological conditions), and an imidazole side chain (which is partially protonated), classifying it as a ...
Histidine is thus able to act as a powerful general base, activating the serine nucleophile. The histidine base aids the first leaving group by donating a proton, and also activates the hydrolytic water substrate by abstracting a proton as the remaining OH − attacks the acyl-enzyme intermediate.
Shuttle catalysis is used to describe catalytic reactions where a chemical entity of a donor molecule is transferred to an acceptor molecule. [1] In these reactions, while the number of chemical bonds of each reactant changes, the types and total number of chemical bonds remain constant over the course of the reaction.
The OH group in the active site acts as a nucleophile to attack the phosphorus in DIFP and form a tetrahedral intermediate and release a proton. Then the P-F bond is broken, one electron is transferred to the F atom and it leaves the intermediate as F − anion. It combines with a proton in solution to form one HF molecule.
Imidazole is the side chain of histidine and is typically used at a concentration of 150 - 500 mM for elution. Histidine or histamine can also be used. Decrease in pH; When the pH decreases, the histidine residue is protonated and can no longer coordinate the metal tag, allowing the protein to be eluted.
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The proton motive force and ATP production can be maintained by intracellular acidosis. [88] Cytosolic protons that have accumulated with ATP hydrolysis and lactic acidosis can freely diffuse across the mitochondrial outer-membrane and acidify the inter-membrane space, hence directly contributing to the proton motive force and ATP production.
The nucleophilic glutamate 165 residue of TPI deprotonates the substrate, [4] and the electrophilic histidine 95 residue donates a proton to form the enediol intermediate. [5] [6] When deprotonated, the enediolate then collapses and, abstracting a proton from protonated glutamate 165, forms the GAP product. Catalysis of the reverse reaction ...