Enzymatic synthesis and antioxidant property of gelatin-catechin conjugates

Gelatin-catechin conjugate was synthesized by the laccase-catalyzed oxidation of catechin in the presence of gelatin. The conjugate had a good scavenging activity against superoxide anion radicals. Moreover, the conjugate showed an amplified inhibition effect on human low density lipoprotein oxidation initiated by 2,2'-azobis(2-amidinopropane)dihydrochloride as a radical generator.     

Enzymatic synthesis of delta sleep-inducing peptide

The delta sleep-inducing peptide was assembled enzymatically from three tripeptide fragments. All the peptide bonds were prepared by either papain- or alpha-chymotrypsin-mediated synthesis. Secondary hydrolysis was suppressed by introducing N alpha-protected amino acid or peptide esters as carboxyl components and using an alkaline pH. The protected nonapeptide was oxidized with ferric chloride to deprotect the C-terminal phenylhydrazide and then hydrogenated. The homogeneous peptide was obtained by reversed phase high-performance liquid chromatography. Comparison of enzymatic and chemical preparations showed no obvious differences.     

Enzymatic peptide synthesis by proline iminopeptidase

Summary Proline iminopeptidase was screened for the enzymatic synthesis of peptides containing Pro. The enzyme was purified from the best strainBacillus brevis, and the partially purified enzyme was used for peptide synthesis from Pro-benzylester and Phe. The dipeptide Pro-Phe was obtained in a 40% yield.     

Enzymatic synthesis of amino acid-sugar alcohol conjugates in organic media

Amino acid-sugar alcohol conjugates were synthesized by a commercial serine protease, Optimase M-440, in organic media. Optimase M-440 showed broad substrate specificity towards N-t-Boc-protected l-amino acids as acyl donors and sugar alcohols as nucleophiles. Among various solvents tested Optimase M-440 showed the highest activity in pyridine. The regioselective acylation of the primary –OH groups of sugar alcohols gave the amino acid conjugates in good yields without byproducts.     

Enzymatic peptide synthesis by new supported biocatalysts

Summary It is well known that proteases can be successfully used for peptide synthesis in aqueous medium or in water-containing organic solvents. Copolymerized of acrylated derivatives of-chymotrypsin and polyethylene glycol (PEG) have been prepared and used as biocatalysts for the synthesis of model peptides in organic solvents containing a very low quantity of water. Trypsin has been similarly treated and used as a new biocatalyst particularly for the coupling of non-specific substrates.     

A convenient method for the synthesis of oligonucleotide-cationic peptide conjugates

A method was developed for the synthesis of oligonucleotide-cationic peptide conjugates in solution phase by disulfide bond formation. Precipitation was avoided by the easily removable triethylammonium trifluoroacetate (TEATFAc) salt which served at the same time as a buffer of the reaction mixture. The fast and high yielding disulfide bond formation was due to the Npys thio protecting and activating group of Cys. A solution of the free 5-thiol modified oligonucleotide obtained from Poly-Pak purification was used for conjugation.     

Facile synthesis of peptide nucleic acids and peptide nucleic acid‐peptide conjugates on an automated peptide synthesizer

Peptide nucleic acids (PNAs) are DNA mimics with a neutral peptide backbone instead of the negatively charged sugar phosphates. PNAs exhibit several attractive features such as high chemical and thermal stability, resistance to enzymatic degradation, and stable binding to their RNA or DNA targets in a sequence‐specific manner. Therefore, they are widely used in molecular diagnosis of antisense‐targeted therapeutic drugs or probes and in pharmaceutical applications. However, the main hindrance to the effective use of PNAs is their poor uptake by cells as well as the difficult and laborious chemical synthesis. In order to achieve an efficient delivery of PNAs into cells, there are already many published reports of peptides being used for transport across the cell membrane. In this protocol, we describe the automated as well as cost‐effective semi‐automated synthesis of PNAs and PNA‐peptide constructs on an automated peptide synthesizer. The facile synthesis of PNAs will be helpful in generating PNA libraries usable, e.g. for high‐throughput screening in biomolecular studies. Efficient synthetic schemes, the automated procedure, the reduced consumption of costly reagents, and the high purity of the products are attractive features of the reported procedure. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Enzymatic synthesis of isotopically labelled serine and tryptophan for application in peptide synthesis

L-[1,2-¹³C₂,¹⁵N]Serine was prepared from [1,2-¹³C₂,¹⁵N]glycine on a gram scale by the use of the enzyme serine hydroxymethyltransferase. The reaction was monitored by ¹³C-NMR spectroscopy. This is the first simultaneously ¹³C- and ¹⁵N-labelled serine isotopomer so far reported. Part of the product was directly converted by tryptophan synthase to L-[1,2-¹³C₂,¹⁵N]tryptophan which could conveniently be purified and isolated as Boc-derivative in a yield of 71%. Most of the serine was isolated similarly but to remove remaining starting material in this case purification by column chromatography was required. © 1997 European Peptide Society and John Wiley & Sons, Ltd. J. Pep. Sci.3: 361–366 No. of Figures: 1. No. of Tables: 0. No. of References: 32     

Enzymatic synthesis of peptide in acetonitrile/supercritical carbon dioxide

Summary The peptide synthesis from N-acetyl-L-tyrosine ethyl ester (Ac-Tyr-OEt) and amino acid amides was realized using -chymotrypsin (CT) in acetonitrile (MeCN) or acetonitrile/supercritical carbon dioxide (SCCO₂) containing small amounts of water. In both solvent systems there was an optimum water content for peptide synthesis, above which peptide hydrolysis became more important. After an incubation for 5 hours, the yields of the peptide was 64% in MeCN and 91% in MeCN/SCCO₂, respectively.     

Enzymatic synthesis of vasoactive intestinal peptide analogs by transglutaminase.

Vasoactive intestinal peptide is an amino acceptor and donor substrate for tissue transglutaminase (TGase) in vitro. This peptide contains a single glutamine residue, Gln16, which was identified as the amino acceptor substrate. Different gamma(glutamyl16)amine derivatives of vasoactive intestinal peptide were synthesized enzymatically in vitro. The modification is very fast when compared with that of many native substrates of TGase. The analogs 1,3-diaminopropane, putrescine, cadaverine, spermidine, spermine, glycine ethyl ester and mono-dansylcadaverine of the peptide were purified by high-performance liquid chromatography on a reverse-phase column and were analyzed by electrospray mass spectrometry. When amines were absent in the assay mixture as an external amino donor, lysine residue occurring in the peptide was an effective amino donor site for TGase. Only one of the three lysine residues of vasoactive intestinal peptide, namely Lys21, was demonstrated to be involved in both inter- and intramolecular cross-link formation.     

Design and synthesis of enediyne–peptide conjugates and their inhibiting activity against chymotrypsin

Novel enediyne–amino acid conjugates 1–4 have been synthesized. All of these effectively target the enzyme chymotrypsin inhibiting its proteolytic activity. The conjugate with a directly linked phenyl alanine is the most effective inhibitor with a K_i of 3 μM. The mode of inhibition is mostly competitive or of a mixed type depending on the nature of the inhibitor.     

New peptide conjugates with 9-aminoacridine: synthesis and binding to DNA.

New peptides-9-aminoacridine conjugates with an ethylene diamine linker-have been synthesized (both solution and solid phase methods were used) and their interactions with DNA have been studied. The affinity of H-Phe-Gln-Gly-Ile(2)-NHCH(2)CH(2)NH-Acr conjugate and of its extended analogue containing 6-aminohexanoic acid to DNA were lower than that of a standard H-Gly-NHCH(2)CH(2)NH-Acr conjugate. The results fit well into our concept of peptide conjugates with lowered binding activity to DNA, which could be capable of unlimited extravascular distribution. Moreover, new structures could be potentially useful as the mild tuners of DNA interaction with strong bis-acridine binders.     

On the synthesis of cyclodextrin–peptide conjugates by the Huisgen reaction

A,D‐substituted cyclodextrin (CDX) substituted on their primary rim side are ideal scaffolds for the macromolecular assembly and formation of templated structures. Their substitution can be achieved through various reactions. However, the use of the well‐known Huisgen reaction in this context is under‐reported. We present here results of the synthesis of model conjugates formed between CDX and representative peptides by click chemistry. Notably, bis‐conjugation of peptides onto a unique scaffold promotes α‐helix formation. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Design and synthesis of peptide conjugates of phosphoramide mustard as prodrugs activated by prostate-specific antigen

A series of Glutaryl-Hyp-Ala-Ser-Chg-Gln-4-aminobenzyl phosphoramide mustard conjugates (1a–e) was designed and synthesized as potential prodrugs for site-specific activation by PSA in prostate cancer cells. All conjugates were found to be substrates of PSA with cleavage occurring between Gln and the para-aminobenzyl (PAB) linker. Structure–activity relationship studies on these conjugates indicated that introduction of electron-withdrawing fluorine(s) on the phenyl ring in the PAB linker uniformly improved the chemical stability of the conjugates while the position of substitution affected differently the self-immolative process of conjugates upon proteolysis. Introduction of a fluorine at ortho position to benzylic phosphoramide as in 1b results in better stability of the conjugate prior to activation while maintaining its antiproliferative activity upon activation by PSA. The conjugate 1b with 2-fluoro substitution was identified as a promising lead for further evaluation and optimization in the development of prostate cancer-targeted prodrugs.     

Enzymatic synthesis of the penicillin and cephalosporin nuclei from an acyclic peptide containing carboxymethylcysteine

The tripeptide delta-(L- carboxymethylcysteinyl )-L-cysteinyl-D-valine (L-CMC-CV) is converted sequentially into the CMC analog of isopenicillin N, the CMC analog of penicillin N, and the CMC analog of desacetoxycephalosporin C by, respectively, isopenicillin N synthetase, isopenicillin N epimerase, and desacetoxycephalosporin C synthetase, all isolated from the beta-lactam producing prokaryote Streptomyces clavuligerus.     

Oxime ligation in acetic acid: efficient synthesis of aminooxy‐peptide conjugates

Oxime ligation is a powerful tool in various bioconjugation strategies. Nevertheless, high reaction rates and quantitative yields are typically reported for aldehyde‐derived compounds. In contrary, keto groups react much slower, with quantitative yields achieved at 5 h for low‐molecular weight compounds and more than 15 h for polymers or dendrimers. In this communication, we report that oxime ligation proceeds rapidly with quantitative (>95%) conversion within 1.5–2 h in pure acetic acid. The practical utility of suggested technique is illustrated by the synthesis of peptide‐steroid and peptide‐polymer conjugates of model aminooxy‐peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Combined thioether/hydrazone chemoselective ligation reactions for the synthesis of glycocluster-antigen peptide conjugates

Hydrazone/thioether ligation reactions show promise for the synthesis of clustered glycosides-antigen conjugates. Due to its propensity to aggregate, tetanus toxoid-derived epitopic peptide TT(830-846) was elected to further evaluate this three-component ligation process. This difficult sequence was supplemented by a hydrazine or a glyoxylyl group either at its C- or N-terminus. The peptide-hydrazines or peptide-aldehydes thus obtained were coupled with glyoxylyl- (or hydrazino-) N-chloroacetylated-L-lysinyl trees and 2-thioethyl-alpha-D-mannopyranoside. As anticipated the ligations were controlled by the nature of the peptide and proved difficult for the C-terminal aldehyde derivative. However, when the process was performed in absence of buffer and using mannitol as a dispersing agent, all combinations finally led to the expected glycoconjugates in 40-60% purified yields.