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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 ...
Chemical formula: C 6 H 9 N 3 O 2 Molar mass: 155.16 g·mol −1 Systematic name: 2-amino-3-(3H-imidazol-4-yl)propanoic acid Abbreviations: H, His Synonyms: Imidazole alanine ({S/D})-α-amino-1H-imidazole-4-propanoic acid
HRG is a glycoprotein of 70-75kDa present at a relatively high concentration in the plasma of vertebrates.The primary structure of human HRG is predicted to be a 507 amino acid multidomain polypeptide consisting of two cystatin-like regions at the N-terminus, a histidine-rich region (HRR) flanked by proline-rich regions (PRR), and a C-terminal domain. [10]
There are several splice variants of H 3 present in various species. Though all of the receptors are 7-transmembrane g protein coupled receptors, H 1 and H 2 are quite different from H 3 and H 4 in their activities. H 1 causes an increase in PIP 2 hydrolysis, H2 stimulates gastric acid secretion, and H3 mediates feedback inhibition of histamine.
The enzyme histidine decarboxylase (EC 4.1.1.22, HDC) is transcribed on chromosome 15, region q21.1-21.2, and catalyzes the decarboxylation of histidine to form histamine. In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission , gastric acid secretion and immune response .
In enzymology, a histidine N-acetyltransferase (EC 2.3.1.33) is an enzyme that catalyzes the chemical reaction. acetyl-CoA + L-histidine CoA + N-acetyl-L-histidine. Thus, the two substrates of this enzyme are acetyl-CoA and L-histidine, whereas its two products are CoA and N-acetyl-L-histidine.
The H 1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors. This receptor is activated by the biogenic amine histamine . It is expressed in smooth muscles , on vascular endothelial cells , in the heart, and in the central nervous system .
HFE. The HFE H63D is a single-nucleotide polymorphism in the HFE gene (c.187C>G, rs1799945), which results in the substitution of a histidine for an aspartic acid at amino acid position 63 of the HFE protein (p.His63Asp).