Peptide formation, enzymatic

Isowa et al. developed an alternative strategy synthesis of protected N5-hydroxy-ornithine from achiral building blocks and enzymatic resolution of the racemic product to its enantiomers 77). The hydroxylamines were protected with tosyl- and benzyl-groups because these protecting groups are stable to the reaction conditions employed in the peptide formation and in the deprotection of the a-amino group. With this key compound, rhodotorulic acid 78>, its enantiomer 78) and ferrichrome 79) were synthesized by straightforward peptide synthesis (Fig. 4a).. ... 

GUI I, Lopez-Fandino R, Jorba X et al. (1996) Biologically active peptides and enzymatic approaches to their production. Enzyme Microb Technol 18 162-183 Grunberg R, Domgall I, Gunther R et al. (2(XX)) Peptide bond formation mediated by substrate mimetics. Eur J Biochem 267 7024-7030... 

Other hand, formation of y-glutamyl peptides by enzymatic transpeptid-ation reactions, also in fermentation broths, is possible (cf. Section VII. 3). 

Borner and coworkers used acid phosphatase to induce microstructure formation. The peptide-segment contained three phosphothreonine residues in the (TV)s peptide motif of the peptide-PEO conjugate, which prevented p-sheet formation. Enzymatic dephosphorylation of the threonine side chains therefore induced self-assembly of the bioconjugate. 

Noda, Y., K. Takai, T. Tokuyama, S. Narumiya, H. Ushiro, and O. Hayaishi Enzymatic Oxidation of Acetyltryptophanamide- and Tryptophan-Containing Peptides. Formation of Dehydrotryptophan. J. Biol. Chem. 252, 4413 (1977). 

In addition to the catalytic action served by the snRNAs in the formation of mRNA, several other enzymatic functions have been attributed to RNA. Ribozymes are RNA molecules with catalytic activity. These generally involve transesterification reactions, and most are concerned with RNA metabofism (spfic-ing and endoribonuclease). Recently, a ribosomal RNA component was noted to hydrolyze an aminoacyl ester and thus to play a central role in peptide bond function (peptidyl transferases see Chapter 38). These observations, made in organelles from plants, yeast, viruses, and higher eukaryotic cells, show that RNA can act as an enzyme. This has revolutionized thinking about enzyme action and the origin of life itself. 

It is interesting to note that serine peptidases can, under special conditions in vitro, catalyze the reverse reaction, namely the formation of a peptide bond (Fig. 3.4). The overall mechanism of peptide-bond synthesis by peptidases is represented by the reverse sequence f-a in Fig. 3.3. The nucleophilic amino group of an amino acid residue competes with H20 and reacts with the acyl-enzyme intermediate to form a new peptide bond (Steps d-c in Fig. 3.3). This mechanism is not relevant to the in vivo biosynthesis of proteins but has proved useful for preparative peptide synthesis in vitro [17]. An interesting application of the peptidase-catalyzed peptide synthesis is the enzymatic conversion of porcine insulin to human insulin [18][19]. 

A practical enzymatic procedure using alcalase as biocatalyst has been developed for the synthesis of hydrophilic peptides.Alcalase is an industrial alkaline protease from Bacillus licheniformis produced by Novozymes that has been used as a detergent and for silk degumming. The major enzyme component of alcalase is the serine protease subtilisin Carlsberg, which is one of the fully characterized bacterial proteases. Alcalase has better stability and activity in polar organic solvents, such as alcohols, acetonitrile, dimethylformamide, etc., than other proteases. In addition, alcalase has wide specificity and both l- and o-amino acids that are accepted as nucleophiles at the p-1 subsite. Therefore, alcalase is a suitable biocatalyst to catalyse peptide bond formation in organic solvents under kinetic control without any racemization of the amino acids (Scheme 5.1). 

DKPs are simple and easy to obtain and are quite common by-products of synthetic, spontaneous, and biological formation pathways. DKP formation has been well documented as side reactions of solid-phase and solution-phase peptide synthesis. In addition, DKPs have been shown to be decomposition products of various peptides, proteins, and other commercial pharmaceuticals. Cyclic dipeptides were found to be present in solutions of human growth hormone, bradykinin, histerlin, and solutions of agents within the classes of penicillins and cephalosporins. " DKPs are also enzymatically synthesized in several protists and in members of the plant kingdom. Hydrolysates of proteins and polypeptides often contain these compounds and they are commonly isolated from yeasts, lichens, and fungi. ... 

The PNA chain was linked to the peptide spacer glutamic acid-(y-tert-butyl ester)-(fi-aminohexanoic acid)-(fi-aminohexanoic acid) (Glu [OtBuj-fiAhx-fiAhx) via an enzymatically cleavable Glu-Lys handle. The Glu [OtBuj-fiAhx-fiAhx spacer was coupled to the amino-functionalized membrane by standard Fmoc-Chemistry. Then the membranes were mounted in an ASP 222 Automated SPOT Robot and a grid of the desired format was dispensed at each position. The free amino groups outside the spotted areas were capped and further chain elongation was performed with Fmoc-protected PNA monomers to synthesize the desired PNA oligomers (18). After completion of the synthesis, the PNA oligomers were cleaved from the solid support by incubation with bovine trypsin solution in ammonium bicarbonate at 37 °C for 3 h. 

Enzymatically active ribonucleic acid segments (some of which are known as ribozymes) with the capacity to catalyze RNA self-splicing or peptide bond formation. The overall catalytic rate enhancement is around 10 ... 

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