Glyco amino acids

Monsigny, M., Quetard, C., Bourgerie, S., Delay, D., Pichon, C., Midoux, P. et al. (1998) Glycotargeting the preparation of glyco-amino acids and derivatives from unprotected reducing sugars. Biochimie, 80, 99-108. 

Fig. 39. Chemical structure of the glyco amino acid extracted from ovomucoid...

Several combinatorial approaches for the synthesis of glyco-amino acids have been developed, due to the complexity of carbohydrate conjugates. The synthetic challenge is to get access to these building blocks by automated synthesis in order to generate glycopeptides library, to fully understand their biological roles and to widen their use in medicinal chemistry. 

SCHEME 10. Synthesis of H2N-(Thr)2-(LacNAc-a-Thr)-(Thr)2-Gly-OH. Conditions (i) H2, Pd(C), MeOH-AcOH (10 1), 1 h (ii) 20% piperidine in DMF (iii) Fmoc-Thr, (benzotriazol-l-yloxy)tripyrrolidi-nophosphonium hexafluorophosphate (PyBOP), IV-hydroxybenzotriazole (HOBt), ethyldiisopropylamine (DIPEA) (iv) Glyco-amino acid 64, PyBOP, HOBt, DIPEA (v) TFA (vi) NaOMe, MeOH. 

The protein was purified by a dialysis procedure, denatured and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Western blotting indicated that the protein of interest consisted of two components, one of which increased in concentration as the purification proceeded. The authors initially suggested that this could be due to the presence of a number of species produced by modification of the amino acid side-chains, for example, by glyco-sylation, or by modification of the C- or N- terminus. 

The hSubunit of Tomato Fruit Polygalacturonase Isoenzyme 1 Defines a New Class of Plant Cell Proteins Involved in Pectin Metabolism AroGPs (Aromatic Amino Acid Rich Glyco Proteins)... 

Prohaska and coworkers61 isolated sialo- and asialo-glyco-octapeptides from glycophorin AM and AN, and recorded their 13C-n.m.r. spectra at 50.3 MHz. Their work will be discussed in relation to other 13C-n.m.r.-spectral studies of a synthetic pentapeptide that has the same amino acid sequence as the N-terminal portion of glycophorin AM (see later). 

K. Aoi, K. Tsutsumiuchi, A. Yamamoto, and M. Okada, Globular carbohydrate macromolecule sugar balls 3. Radial-growth polymerization of sugar-substituted x-amino acid N-carboxyanhydrides (glyco-NCAs) with a dendritic initiator, Tetrahedron, 53 (1997) 15415-15427. 

The two most important bile acids, cholic acid C24H40Os and desoxy-cholic acid C24H40O4, occur in ox bile in combination, partly with glycine and partly with taurine as glyco- and taurocholic and glyco- and tauro-desoxycholic acids. The linkage between the amino acids and the bile acids is of an amide nature. On hydrolysis the nitrogenous constituents are split off. 

AMINO ACIDS, PEPTIDES PROTEINS Recommended nomenclature and symbolism for amino acids and peptides J. Biol Chem. (1985) 260, 14-42 Biochemistry (1975) 14, 449-462 Abbreviations and symbols for the description of the conformation of polypeptide chains /. Biol Chem. (1970) 245, 6489-6497 Nomenclature of iron-sulfur proteins Eur. J. Biochem. (1979) 93, 427-430 Corrections Eur. J. Biochem. (1979) 102, 315 Nomenclature of peptide hormones J. Biol Chem. (1975) 250, 3215-3216 Nomenclature of human immunoglobulins Eur. J. Biochem. (1974) 45, 5-6 Recommended nomenclature of glycoproteins, glyco-peptides, and peptidoglycans /. Biol Chem. (1987) 262, 13-18 Recommended nomenclature of electron-transfer proteins... 

Amino acids with modified side-chains are frequently encountered in biological systems. Among all the modifications involving the side-chain of the amino acids, reversible glyco-sylation and phosphorylation play a central role in regulating the biological functionalities of numerous proteins. 

PTMs, such as methylation or acetylation or addition of complex N- or O-linked glyco-sylations, are covalently bound modifications to one or several amino acid residues. This can drastically affect the outcome of the altered protein (Mann and Jensen, 2003). Genomic information, at present, cannot predict the processes of PTM and cannot be studied with genomic techniques. With protein modification, being an important area of parasitic flat-worm proteomics, the most effective method to research them is with mass spectrometry (Mann et al., 2001). 

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