Protein Hydroxylation

Scheme 14 Protein hydroxylation. Hydroxylations occur at the 3- or 4-position of proiine, the 5-position of iysine, and the 3-position of asparagine.

Kivirikko KI, Myllyla R, Pihlajaniemi T (1989), Protein hydroxylation prolyl 4-hydroxylase, an enzyme with four cosubstrates and a multifunctional subunit. FASEB J. 3 1609-1617. 

The hydroxylation of certain proteins occurs by the addition of the OH group to proline and lysine residues in the protein. Hydroxylation is mediated in the presence of vitamin C as a cofactor for the respective hydroxylases. Other proteins may undergo carboxylation of glutamine residue. This process requires vitamin K as a cofactor. 

Hydrogenated coconut acid Hydrogenated menhaden acid Hydrolyzed casein Hydrolyzed milk protein Hydroxylated lanolin Hydroxylated lecithin Hydroxystearic acid Isobutyl oleate lsodeceth-5 Isopropyl oleate Isostearamidopropyl dimethylamine Isostearamidopropyl PG-dimonium chloride lsosteareth-2 lsosteareth-10 lsosteareth-20 Isostearyl palmitate Lanolin wax Lapyrium chloride Lauramidopropyl dimethylamine Lauramidopropyl PEG-dimonium chloride phosphate... 

Hydrolyzed milk protein Hydroxylated lanolin Hydroxypropylcellulose Hydroxypropyl methylcellulose Phenyl trimethicone Polyquaternium-1 Propylene glycol alginate Quaternium-22 Rice (Oryza sativa) starch Shellac wax Silicone emulsion Sodium hyaluronate ... 

There are various chemical functional groups that would attract and sequester the metals in biomass acetamido groups of chitin, structural polysaccharides of fungi, amido, amino, sulphydryl and carboxyl groups in proteins, hydroxyls in polysaccharide and mainly carboxyls and sulfates in polysaccharides of marine algae that belong to the divisions Phaeophyta, Rhodophyta and Chlorophyta. 

While electrospray is used for molecules of all molecular masses, it has had an especially marked impact on the measurement of accurate molecular mass for proteins. Traditionally, direct measurement of molecular mass on proteins has been difficult, with the obtained values accurate to only tens or even hundreds of Daltons. The advent of electrospray means that molecular masses of 20,000 Da and more can be measured with unprecedented accuracy (Figure 40.6). This level of accuracy means that it is also possible to identify post-translational modifications of proteins (e.g., glycosylation, acetylation, methylation, hydroxylation, etc.) and to detect mass changes associated with substitution or deletion of a single amino acid. 

Amino acid-derived hormones include the catecholamines, epinephrine and norepinephrine (qv), and the thyroid hormones, thyroxine and triiodothyronine (see Thyroid AND ANTITHYROID PREPARATIONS). Catecholamines are synthesized from the amino acid tyrosine by a series of enzymatic reactions that include hydroxylations, decarboxylations, and methylations. Thyroid hormones also are derived from tyrosine iodination of the tyrosine residues on a large protein backbone results in the production of active hormone. 

The biosynthesis process, which consists essentially of radical coupling reactions, sometimes followed by the addition of water, of primary, secondary, and phenohc hydroxyl groups to quinonemethide intermediates, leads to the formation of a three-dimensional polymer which lacks the regular and ordered repeating units found in other natural polymers such as cellulose and proteins. 

STMP reacts with other nucleophiles such as aqueous ammonia to yield amidophosphates, which contains a P—N bond. STMP is used for the modification of the physical properties of starch and proteins by reaction with the amino and hydroxyl groups. 

Hydroxylated amino acids (eg, 4-hydroxyproline, 5-hydroxylysine) and A/-methylated amino acids (eg, /V-methylhistidine) are obtained by the acid hydrolysis of proteins. y-Carboxyglutamic acid occurs as a component of some sections of protein molecules it decarboxylates spontaneously to L-glutamate at low pH. These examples are formed upon the nontranslational modification of protein and are often called secondary protein amino acids... 

One of the important consequences of neuronal stimulation is increased neuronal aerobic metabolism which produces reactive oxygen species (ROS). ROS can oxidize several biomoiecules (carbohydrates, DNA, lipids, and proteins). Thus, even oxygen, which is essential for aerobic life, may be potentially toxic to cells. Addition of one electron to molecular oxygen (O,) generates a free radical [O2)) the superoxide anion. This is converted through activation of an enzyme, superoxide dismurase, to hydrogen peroxide (H-iO,), which is, in turn, the source of the hydroxyl radical (OH). Usually catalase... 

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