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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 ...
The two main systems in humans are the glycerol phosphate shuttle and the malate-aspartate shuttle. The malate/a-ketoglutarate antiporter functions move electrons while the aspartate/glutamate antiporter moves amino groups. This allows the mitochondria to receive the substrates that it needs for its functionality in an efficient manner. [1]
The endothelial protease vasohibin [f] uses a cysteine as the nucleophile, but a serine to coordinate the histidine base. [43] [44] Despite the serine being a poor acid, it is still effective in orienting the histidine in the catalytic triad. [43] Some homologues alternatively have a threonine instead of serine at the acid location. [43]
Taken together, import of ADP and Pi and export of the resulting ATP results in one proton imported, subtracting from the number available for use by the ATP synthase directly. Taking this into account, it takes 8/3 +1 or 3.67 protons for vertebrate mitochondria to synthesize one ATP in the cytoplasm from ADP and Pi in the cytoplasm.
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.
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.
The net effect of the malate–aspartate shuttle is purely redox: NADH in the cytosol is oxidized to NAD +, and NAD + in the matrix is reduced to NADH. The NAD + in the cytosol can then be reduced again by another round of glycolysis, and the NADH in the matrix can be used to pass electrons to the electron transport chain so ATP can be synthesized.
In enzymology, histidinol dehydrogenase (HIS4) (HDH) (EC 1.1.1.23) is an enzyme that catalyzes the chemical reaction. L-histidinol + 2 NAD + L-histidine + 2 NADH + 2 H +. Thus, the two substrates of this enzyme are L-histidinol and NAD +, whereas its 3 products are L-histidine, NADH, and H +.