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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 ...
A typical characteristic of histidinemia is an increase in the blood histidine levels from normal levels (70–120 μM) to an elevated level (290–1420 μM). [3] Further testing includes: observing histidine as well as imidazolepyruvic acid metabolites in the urine. However, neonatal urine testing has been discontinued in most places, with the ...
Since human blood is slightly basic (with a normal pH range of 7.35 to 7.45) therefore the predominant form of histamine present in human blood is monoprotic at the aliphatic nitrogen. Histamine is a monoamine neurotransmitter .
Carnosine is a dipeptide composed of beta-alanine and histidine, and is found in skeletal muscle and cells of the nervous system. [6] This disorder results in an excess of carnosine in the urine, cerebrospinal fluid, blood, and nervous tissue. [7]
Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase. [8] [9] The word haem is derived from Greek αἷμα haima 'blood'.
Found in many annelids, including earthworms, it is a giant free-floating blood protein containing many dozens—possibly hundreds—of iron- and heme-bearing protein subunits bound together into a single protein complex with a molecular mass greater than 3.5 million daltons. Leghemoglobin
Iron is transported by transferrin whose binding site consists of two tyrosines, one aspartic acid and one histidine. [22] The human body has no controlled mechanism for excretion of iron. [23] This can lead to iron overload problems in patients treated with blood transfusions, as, for instance, with β-thalassemia.
This histidine-rich glycoprotein contains two cystatin-like domains and is located in plasma and platelets.It is known that HRG binds heme, dyes, and divalent metal ions and it is thought to have multiple roles in the human blood, including roles in immunity, angiogenesis and coagulation. [15]