Amino acid carbonyl group

Specificity Each of these enzymes has a different specificity for the amino acid R-groups adjacent to the susceptible peptide bond (Figure 19.5). For example, trypsin cleaves only when Ihe carbonyl group of the peptide bond is contributed by arginine or lysine. These enzymes, like pepsin described above, are synthesized and secreted as inactive zymogens. 

The free glycine ethyl ester nucleophilically attacks the mixed anhydride specifically at the amino acid carbonyl, rather than the carbethoxycarbonyl group, liberating carbon dioxide and ethanol and forming the acylated dipeptide ester in good yield. 

All aliphatic compounds containing primary or secondary amine group react in browning reaction but at different rates depending upon the molecular structure. The reactivity of the reactants (amino acids, carbonyl compounds) in the browning reaction had been reported in the literature as ... 

The precursor to an amino acid prepared by enantioselective hydrogenation has a Z double bond conjugated with a carboxylic acid carbonyl group. 

Fig. 7. Oxidation products of proteins. The vertical structure in the middle represents the main peptide chain with amino acid side groups extending horizontally (M2). The a-carbons in the primary chain can be oxidized to form hydroperoxides. Reactions on the right side near the top exemplify oxidation of the primary chain leading to a peroxyl radical. Side chains represented are lysine, methionine, tyrosine, cysteine, and histidine, top to bottom, respectively. Modifications of the side chains and primary chain lead to carbonyl formation and charge modifications. If these reactions are not detoxified by antioxidants, they may propagate chain reactions within the primary chain, leading to fragmentation of the protein. See the text for details, o, represents reaction with oxygen RNS, reactive nitrogen species ROS, reactive oxygen species. Dense dot represents unpaired electron of radical forms.

The complexings of D-glucose, D-fructose, and maltose with borate anions have been studied by polarimetric, conductivity, and pH measurements, and circular dichroism methods have been used to investigate the complexing of cuprammonium ions with carbohydrate diols and amino-alcohols. An examination of the c.d. spectra of fifteen methyl 3-acetamido-3,6-dideoxyhexopyranoside derivatives measured in methanol, 2,2,2-trifluoroethanol, and acetonitrile su ests that the amide group is not completely planar and may show chirality. The n it transition of the carboxylic acid carbonyl groups at... 

Deamination of amino acids by carbonyl compounds has long been known in organic chemistry. Classical instances are the Strecker reaction of amino acids with alloxan and rimilar reactions with o-quinones, isatin, ninhydrin, methylglyoxal, and the like. In such cases deamination is usually associated with decarboxylation of the amino acid. Condensation of the amino and carbonyl groups to yield SchiiTs bases, and tautomeric transformation of these, are generally assumed as intermediary steps. 

We have now completed our survey of the basic organic chemistry compound classes, as defined by simple functional groups. In the remainder of the book, we shall examine compounds with multiple functional groups, whether they be the same or different. We shall see the amino group and amine derivatives again in these chapters, particularly when studying heterocycles, proteins, and nucleic acids. We shall learn that the combination of the amino and carbonyl groups underlies the molecular structure of life itself. 

The most general methods for the syntheses of 1,2-difunctional molecules are based on the oxidation of carbon-carbon multiple bonds (p. 117) and the opening of oxiranes by hetero atoms (p. 123fl.). There exist, however, also a few useful reactions in which an a - and a d -synthon or two r -synthons are combined. The classical polar reaction is the addition of cyanide anion to carbonyl groups, which leads to a-hydroxynitriles (cyanohydrins). It is used, for example, in Strecker s synthesis of amino acids and in the homologization of monosaccharides. The ff-hydroxy group of a nitrile can be easily substituted by various nucleophiles, the nitrile can be solvolyzed or reduced. Therefore a large variety of terminal difunctional molecules with one additional carbon atom can be made. Equally versatile are a-methylsulfinyl ketones (H.G. Hauthal, 1971 T. Durst, 1979 O. DeLucchi, 1991), which are available from acid chlorides or esters and the dimsyl anion. Carbanions of these compounds can also be used for the synthesis of 1,4-dicarbonyl compounds (p. 65f.). 

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