What is the function of histidine in the human body?
Histidine is required for synthesis of proteins. It plays particularly important roles in the active site of enzymes, such as serine proteases (e.g., trypsin) where it is a member of the catalytic triad. Excess histidine may be converted to trans-urocanate by histidine ammonia lyase (histidase) in liver and skin.
How does histidine act as a buffer?
In a histidine proton shuttle, histidine is used to quickly shuttle protons. It can do this by abstracting a proton with its basic nitrogen to make a positively charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen.
Where is histidine found in the human body?
Histidine structure An abundant source of histidine is hemoglobin, which contains 8.5%. The human body is unable to synthesize this amino acid, so it must be obtained through dietary means. Figure 1 Protonation states of Histidine.
Is histidine a buffering capacity?
Histidine has a pKa of 6.2. However, this pKa changes when the histidine is bound to other amino acids resulting in a pKa range of 5-8 (Abe, 2000). At physiological pH’s, histidine is the major buffering component of proteins.
What is histidine buffer?
Histidine buffer has a concentration of 0.1M and a pH of 6.0. Histidine makes a good amino acid buffer under physiological conditions, not under very acidic or very basic conditions, and is the best amino acid buffer within its buffering range. For laboratory use only.
Why does histidine show buffering capacity at physiological pH?
The pKa of histidine is 6.0, so histidine is best at buffering at pH 6.0. The acidic amino acids have pKa’s below histidine’s, and the basic amino acids have pKa’s far above histidine’s, such that the pKa of histidine is the closest to pH 7.4 of any of the amino acids.
Why is histidine a good buffer at physiological pH?
What is histidine residue?
histidine residue (CHEBI:32535) is a α-amino-acid residue (CHEBI:33710) histidine residue (CHEBI:32535) is conjugate base of histidinium residue (CHEBI:32536) histidine residue (CHEBI:32535) is substituent group from histidine (CHEBI:27570)
What is the buffering range of histidine?
The effective buffering range of histidine is pH 5.12 to pH 7.12 and pH 8.45 to pH 10.45.
At which pH are glycine and histidine used good buffers?
8.6-to-10.6
A solution of a weak acid or base is effective in buffering pH when the pH is ± 1 unit from the pKa. In this pH range, appreciable amounts of both conjugate base and conjugate acid species are present in solution. Therefore, glycine can be used as an effective buffer in the pH range of 8.6-to-10.6.
Why histidine is pH sensitive?
Histidine (His) is composed of an imidazole group, a carboxyl group, and an amino group27 and it is regarded as being pH-sensitive because the imidazole ring has an electron lone pair on the unsaturated nitrogen that makes His amphoteric by protonation-deprotonation28.
At what pH is histidine neutral?
pH 7.4
The imidazole group of histidine is the only amino acid side chain affected within this range. At pH 5.0 the group is positively charged, polar, and hydrophilic, whereas at pH 7.4 it is neutral, apolar, and hydrophobic.
How is histidine synthesized in the human body?
Histidine is required as a precursor of carnosine in human muscle and parts of the brain where carnosine appears to play an important role as a buffer and antioxidant. It is synthesized in the tissue by carnosine synthase from histidine and β-alanine, at the expense of ATP hydrolysis.
Are there any Alternative buffers to excipients for histidine?
Histidine, tromethamine and a number of other alternative buffers offer advantages over conventionally used excipients. The use of these alternative buffers can do nothing but help to augment the tools formulators have and may enable the development of a therapeutic that otherwise may have failed.
Why are histidine amino acids used in protein therapy?
Histidine, an essential amino acid, is becoming increasingly common in formulations of protein therapeutics. Having a pKa of 6.1, it is ideal for the protein formulations near neutral conditions (Table 2). Histidine has been shown to protect a monoclonal antibody in both the liquid and lyophilised state against heat stress 23-25.
Who was the first person to discover histidine?
Histidine is an alpha-amino acid with an imidazole functional group. It is one of the 22 proteinogenic amino acids. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans and other mammals.