Glycyl amino acids

The AAA thus has two photometers in series. Since for every eluting amino acid both signals are recorded, the so-called 570/440 absorbance ratio may be of help in the identification process. As an example the simple primary amino acids have a 570/440 ratio of approximately 6, whereas the sulfur amino acids (cystine, sulfocysteine) have much lower ratios, approaching a value of 1. Small peptides and glycyl-amino acids will react with ninhydrin, an important fact for the diagnosis of prolidase deficiency and aspartylglycosaminuria. 

Cobalt(ll) forms many complexes which can exhibit oxygen-carrying properties (2,19). Reversible oxygen uptake in solutions of cobalt (ll)-histidine (33-36), and cobalt (II) in the presence of a-amino acids and peptides (37—39) has been known for some time. The reaction of cobalt (II) with dipeptide was first observed in enzymic studies involving glycyl-glycine (40). 

The realization of the widespread occurrence of amino acid radicals in enzyme catalysis is recent and has been documented in several reviews (52-61). Among the catalytically essential redox-active amino acids glycyl [e.g., anaerobic class III ribonucleotide reductase (62) and pyruvate formate lyase (63-65)], tryptophanyl [e.g., cytochrome peroxidase (66-68)], cysteinyl [class I and II ribonucleotide reductase (60)], tyrosyl [e.g., class I ribonucleotide reductase (69-71), photosystem II (72, 73), prostaglandin H synthase (74-78)], and modified tyrosyl [e.g., cytochrome c oxidase (79, 80), galactose oxidase (81), glyoxal oxidase (82)] are the most prevalent. The redox potentials of these protein residues are well within the realm of those achievable by biological oxidants. These redox enzymes have emerged as a distinct class of proteins of considerable interest and research activity. 

Racemization is not encountered when 4-unsubstituted-5(477)-oxazolones or 4,4-disubstituted-5(477)-oxazolones are used as reagents. Indeed, 4-unsubstituted-5(47/)-oxazolones function as glycine synthons in the synthesis of A-acylglycyl-a-amino acids. For example, aminolysis of 2-(trifluoromethyl)-5(47/)-oxazolone with a-methylphenylalanine affords A-(trifluoroacetyl)glycyl-a-methylphenylalanine. 4,4-Disubstituted-5(4//)-oxazolones, readily available by alkylation of the monosubstituted derivatives, are very useful intermediates in the synthesis of peptides that incorporate ot,ot-disubstituted amino acids. As an example, 4-(aryl-methyl)-2-phenyl-4-(trifluoromethyl)-5(4//)-oxazolones 260 are key intermediates... 

RIS theory, in the form appropriate for branched molecules, is used to calculate the mean-square unperturbed radius of gyration, < s2>0, for cross-linked polyglycine, poly(L-alanine),poly(L-proline),poly(i-alanyl-D-alanine),poly(i.-prolyl-L-pro lylglycine),poly(L-prolyl-i.-alanylglycine ,poly(glycyl-L-alanyl-L-pro line), andpoly(L-aianyl-L-alanylgIycine).Thecentral amino acid residue in each polypeptide chain is replaced by the L-cysteinyl residue involved in cross-link formation. Each cross-linked molecule is considered to contain two trifunctional branch points, the a-carbon atoms of the two... 

Benzylsuccinate synthase has an amino acid sequence homologous to that of pyruvate formate lyase (p. 799 -801), contains a glycyl radical, and is activated in a manner similar to activation of pyruvate formate lyase. Propose a mechanism for formation of benzylsuccinate. See Krieger et al.383... 

Chiral a-amino acids The lithium anion of the N-protected glycine amides 3, prepared by reaction of the pyrrolidine with [bis(methylthio)methylene]glycyl pivalic anhydride (DMAP), is alkylated with high diastereoselectivity. The (S)-amino acid (5) is obtained on acid hydrolysis. 

Several different types of chiral additives have been used including (IR)-(-)-ammonium-IO-camphorsulfonic acid, cyclodextrins. proteins, and various amino acid derivatives such as //-benzoxycarbonyl-glycyl-L-proline as well as macrocyclic antibiotics. 

Formally, however, the amino acids contained either in peptides or proteins are named in a fashion related to that used for alkanes. The -ine suffix is replaced by -yl to give, for GAG, glycyl-alanyl-glycine. Peptide and protein sequences are always written and named from the N-terminus to the C-terminus. The C-terminal amino acid retains its full name. 

Synthesis of peptides from amino acids in the solid state or in aqueous solution has been reported with the aid of ATP, Mg2 and free imidazole 34 36). a 4.5 % yield of glycine peptides has been reported in the solid state, 0.6 % yield in aqueous solution 36). Gly-N-pA is formed in a yield of 72.5 % from glycine and chemically synthesized ImpA in aqueous solution, pH 8.0, at room temperature 37). At initial of pH 6.0 glycyl 5 -adenylate (gly-O-pA) and 2 (3 )-0-glycyl adenosine 5 -phosphate (pA-g W are formed 37). 

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