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Histidine ball and stick model spinning. 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 ...
An aromatic amino acid is an amino acid that includes an aromatic ring. Phenylalanine Among the 20 standard amino acids , histidine , phenylalanine , tryptophan , tyrosine , are classified as aromatic.
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]
Aromatic acids are a type of aromatic compound. Included in that class are substances containing an aromatic ring and an organic acid functional group. There are several categories of aromatic acids including: Phenolic acids: substances containing an aromatic ring and an organic carboxylic acid function (C6-C1 skeleton). Aromatic amino acids [1]
The type I copper does not bind O 2, but functions solely as an electron transfer site. The type I copper center consists of a single copper atom that is ligated to a minimum of two histidine residues and a single cysteine residue, but in some laccases produced by certain plants and bacteria, the type I copper center contains an additional ...
Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated." [1] The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were understood. The current definition of aromatic compounds does not have any relation to their odor.
^a EINECS number 206-513-8 (L-histidine) ^a CID 71083 from PubChem (D-histidine) ... Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; ...
Colleagues, histidine should be aromatic. It obeys aromaticity rules, exhibits aromatic properties and, no surprise, is aromatic. The reason above why Lehninger did not count it as aromatic is kinda tradition - aromatic aa supposed to have a moderate absorption at 260-300 nm region. It is pretty trivial and has nothing to do with chemistry.