Asparagine

Abstract: The discovery of the adventitious formation of the potential cancer-causing agent acrylamide in a variety of foods during cooking has raised much concern, but the chemical mechanism(s) governing its production are unclear. Here we show that acrylamide can be released by the thermal treatment of certain amino acids (asparagine, for example), particularly in combination with reducing sugars, and of early Maillard reaction products (N-glycosides). Our findings indicate that the Maillard-driven generation of flavour and colour in thermally processed foods can -- under particular conditions -- be linked to the formation of acrylamide.

Abstract: The addition of a carbohydrate moeity to the side chain of a residue in a protein chain in uences the physicochemical properties of the protein Gly cosylation is known to alter proteolytic resistance protein solubility stability local structure lifetime in circulation and immunogenicity Of the various forms of protein glycosylation found in eukaryotic systems the most important types are N linked O linked GalNAc mucin type and O linked GlcNAc intracellular nuclear glycosylation N linked glycosylation is a co translational process involving the transfer of the precursor oligosac charide GlcNAc Man Glc to asparagine residues in the protein chain The asparagine usually occurs in a sequon Asn Xaa Ser Thr where Xaa is not Proline This is however not a speci c consensus since not all such sequons are modi ed in the cell O linked glycosylation involves the post translational transfer of an oligosaccharide to a serine or threonine residue In this case there is no well de ned motif for the acceptor site other than the near vicinity of proline and valine residues We have developed glycosylation site prediction methods for these three types of glycosylation using arti cial neural networks that examine correla tions in the local sequence context and surface accessibility In this paper we have used glycosylation site information on human proteins to illustrate the contribution of glycosylation to protein function and assess how widespread this modi cation is across the human proteome

Abstract: Nitrogen assimilation is a vital process controlling plant growth and development. Inorganic nitrogen is assimilated into the amino acids glutamine, glutamate, asparagine, and aspartate, which serve as important nitrogen carriers in plants. The enzymes glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), aspartate aminotransferase (AspAT), and asparagine synthetase (AS) are responsible for the biosynthesis of these nitrogen-carrying amino acids. Biochemical studies have revealed the existence of multiple isoenzymes for each of these enzymes. Recent molecular analyses demonstrate that each enzyme is encoded by a gene family wherein individual members encode distinct isoenzymes that are differentially regulated by environmental stimuli, metabolic control, developmental control, and tissue/cell-type specificity. We review the recent progress in using molecular-genetic approaches to delineate the regulatory mechanisms controlling nitrogen assimilation into amino acids and to define the physiological role of each isoenzyme involved in this metabolic pathway.