China
Africa
Explore chapters and articles related to this topic
The Modification Of Tyrosine
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
An interesting effect of substrate on the reaction of an enzyme with tetranitromethane has been reported by Christen and Riordan.61 Generally, protection of an enzyme from loss of activity secondary to chemical modification with the concomitant lack of modification of an amino acid residue is observed in the presence of substrate. Christen and Riordan, however, observed that aspartate aminotransferase was readily inactivated by tetranitromethane only in the presence of both substrates, glutamate and α-keto-glutarate (“syncatalytic” modification). This inactivation was associated with the modification of an additional tyrosyl residue.
Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
Acylation of one tyrosine (and five amino groups) in goat a-lactalbumin results in 15% loss of lactose synthetase activating activity and 10% loss in galactose transferase activating activity.345 Slightly higher (approximately 25%) losses in lactose synthetase activating ac- tivity seem to occur when the enzyme is modified to the same extent by using tetranitro- methane or triiodide.346 α -Lactalbumin also tends to polymerize when treated with tetranitromethane.
The Modification of Tyrosine
Published in Roger L. Lundblad, Claudia M. Noyes, Chemical Reagents for Protein Modification, 1984
Roger L. Lundblad, Claudia M. Noyes
An interesting effect of substrate on the reaction of an enzyme with tetranitromethane has been reported by Christen and Riordan.66 Generally, protection of an enzyme from loss of activity secondary to chemical modification with the concomitant lack of modification of an amino acid residue is observed in the presence of substrate. Christen and Riordan, however, observed that aspartate aminotransferase was readily inactivated by tetranitromethane (Figure 27) only in the presence of both substrates, glutamate and α-keto-glutarate (“syncatalytic” modification). This inactivation was associated with the modification of an additional tyrosyl residue. The modified enzyme has some interesting spectral properties (Figures 28 and 29).
Molecular effects of ozone on amino acids and proteins, especially human hemoglobin and albumin, and the need to personalize ozone concentration in major ozone autohemotherapy
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Fouad Mehraban, Arefeh Seyedarabi
Because the ratio of Tyr to Trp residues is 18:1 and Tyr residues have a more uniform distribution, a study of Tyr residues could reveal structural changes in HSA due to ligand binding or other interventions [124]. When the reactivity of Tyr residues in HSA was investigated by nitration with tetranitromethane, Tyr 411, which has a specific indole and benzodiazepine binding site, was found to have 20-fold reactivity compared to the 17 other Tyr residues [125]. Therefore, studying the intrinsic fluorescence behavior of Tyr residues with the possibility of forming di-Tyr crosslinks at inappropriate ozone concentrations that could result in reduced binding capacity of HSA could provide significant and useful information.