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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 ...
Acid–base homeostasis is the homeostatic regulation of the pH of the body's extracellular fluid (ECF). [1] The proper balance between the acids and bases (i.e. the pH) in the ECF is crucial for the normal physiology of the body—and for cellular metabolism. [1]
The normal concentration of 3-methylhistidine in the urine of healthy adult humans has been detected and quantified in a range of 3.63–69.27 micromoles per millimole (μmol/mmol) of creatinine, with most studies reporting the average urinary concentration between 15 and 20 μmol/mmol of creatinine. [1]
See Amino acid for the pK a values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy. The table below lists the model pK a values that are often used in a protein pK a calculation, and contains a third column based on protein ...
The triad of cytomegalovirus protease [b] uses histidine as both the acid and base triad members. Removing the acid histidine results in only a 10-fold activity loss (compared to >10,000-fold when aspartate is removed from chymotrypsin). This triad has been interpreted as a possible way of generating a less active enzyme to control cleavage ...
In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase [1] whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (EC 2.7.11.11). PKA has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism.
Histamine is derived from the decarboxylation of the amino acid histidine, a reaction catalyzed by the enzyme L-histidine decarboxylase. It is a hydrophilic vasoactive amine. Conversion of histidine to histamine by histidine decarboxylase