Hydroxyproline Hyp

Very few post-translational modifications have been found on tropoelastin. However, hydroxylation of 25% of the proline residues is observed [10]. The enzymatic modification of proline to hydroxyproline (Hyp) is performed by prolyl hydroxylase [11]. The purpose of this hydroxylation remains unclear and it is even proposed that Hyps in tropoelastin are a by-product of collagen hydroxylation as this occurs in the same cellular compartment [8]. 

Collagen is the quantitatively most important protein in mammals, making up about 25% of the total protein. There are many different types of collagen, particularly in connective tissue. Collagen has an unusual amino acid composition. Approximately one-third of the amino acids are glycine (Gly), about 10% proline (Pro), and 10% hydroxyproline (Hyp). The... 

The name hydroxyproline (Hyp) is used to refer to the most common naturally occurring form, i.e. (25,47 )-4-hydroxyproline (4). Because of the two chiral C-atoms, this amino acid exists in four epimeric forms. The 2S,4R- and 21 ,45 forms are referred to as trans-hydro-xyprolines and the 25,45- and 27 ,47 forms as c/j-hydroxyprolines or u/Zo-hydroxyprolines. As expected from their configuration, the ds-4-hydroxyprolines can form lactones. 

One-third of the amino acid residues in collagen are Gly, while another quarter are Pro. The hydroxylated amino acids 4-hydroxyproline (Hyp) and 5-hydroxylysine (Hyl) are formed post-translationally by the action of proline hydroxylase and lysine hydroxylase. These Fe2+-containing enzymes require ascorbic acid (vitamin C) for activity. In the vitamin C deficiency disease scurvy, collagen does not form correctly due to the inability to hydroxylate Pro and Lys. Hyl residues are often post-translationally modified with carbohydrate. 

IUPAC abbreviations are employed those for less common residues such as 4-hydroxyproline (Hyp) are included in the text f-butyloxycarbonyl butyl benzyl... 

For calculation of possible amino acid substitutions, the 20 most common amino acids were used together with y-carboxyglutamate (Gla) and hydroxyproline (Hyp) which are commonly found in conotoxins (14). 

Recent studies on separation optimization showed that accurate control of mobile phase pH was essential to successfully resolve a number of important non-hydrolysate amino acids. With good control of a complex gradient profile the system could resolve a mixture of amino acids including, Asn, Gin, cysteine derivatives carboxymethyl cysteine and pyridylethyl cysteine, and the hydroxylated amino acids hydroxyproline (Hyp) and hydroxylysine (Hyl) as well as the hydrolysate amino acids (4). However, the required precision in the control of eluent pH unnecessarily complicated transfer of the method between laboratories. The method also lacked the ability to separate Orn from the hydrolysate amino acids. The current study demonstrates the utility of quaternary HPLC gradient systems for facilitating methods development and simplifying routine eluent preparation with excellent pH control. 

However, in addition to the presence of disulfide bonds, most conopeptide sequences exhibit a high degree of additional posttranslational modifications (PTMs), which include carboxylation of glutamate to form carboxyglutamate and hydroxylation of proline, lysine, and D-valine to form 7-hydroxyproline (Hyp), -hydroxylysine, and D-7-hydroxyvaline, respectively. Other PTMs include epimerization of L-amino acids to form their respective D-amino acid counterparts, halogenation of tryptophan to produce 5-Br-tryptophan... 

E. Extraction and Analysis of Hydroxyproline (Hyp)-Rich Glycoprotein(s) (Extensin)... 

Further the protein content of the AIR varies with the maturity of the tissues, high in immature and low in mature tissues. Since pronase tends to degrade some of the hydroxyproline (hyp)-poor cell wall glycoproteins and possibly portions of the hyp-rich glycoproteins, pronase-treated residues may not give as much useful information on wall glycoproteins compared with the alternative methods described in this article. 

E. EXTRACTION AND ANALYSIS OF HYDROXYPROLINE (HYP)-RICH GLYCOPROTEIN(S) (EXTENSIN)... 

Hydroxyproline (Hyp) can be incorporated into peptides without side-chain protection. The rBu side-chain protecting group has been used for Hyp in Fmoc SPPS [63]. The 3-nitro-2-pyridinesulfenyl (Npys) group for Hyp, Ser, and Thr is compatible with A -Boc and Fmoc protection but has not been widely utilized for synthesis on the solid support. Preparation is via Npys-Cl in the presence of base [64] (Scheme 16). 

Collagen is a protein comprised of three polypeptides (a chains), each having a general amino acid sequence of (-Gly-X-T-) , where X is any other amino acid and is frequently proline (Pro) and Y is any other amino acid and is frequently hydroxyproline (Hyp). A typical amino acid composition of collagen is shown in Table 43.1. The application of helical diffraction theory to high-angle collagen x-ray... 

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