Proline Bond Research Articles

Secondary structure of peptides. 17—Cis/trans isomerism of solid proline‐containing oligopeptides as revealed by 13C NMR CP/MAS spectroscopy

AbstractThe 75.4 MHz 13C NMR CP/MAS spectra of five classes of solid proline peptides were measured: cyclodipeptides, unprotected dipeptides, N‐tert‐butoxycarbonyl‐ (Boc) or N‐benzyloxycarbonyl‐ (Z)‐proline derivatives and N‐protected peptides with an aminoacyl—proline bond. In the case of solid N‐protected proline derivatives, the shift difference (Δδ) of the C‐β and C‐γ signals mainly reflects the cis/trans isomerism of the XPro bond, with Δδ = 3‐5 ppm being characteristic of trans and 7‐11 ppm of cis isomers. However, in the case of solid cyclodipeptides and unprotected dipeptides, the individual crystal lattices also affect the conformation of the side chain, so that the C‐β and C‐γ‐signals are not reliable indicators of the cis/trans isomerism.When the N‐protected proline derivatives were crystallized slowly from various solvents, the N‐Boc‐ and N‐Z‐proline derivatives exclusively yielded the cis isomer, even when the cis/trans equilibrium in solution favoured the trans isomer. In the case of N‐aminoacylprolines, the trans isomer crystallized almost exclusively. Oligopeptides containing two proline units, such as ZProProOH or ZGlyProGly GlyProAlaOH, may possess a cis and a trans bond in the same molecule.

Proline iminopeptidase from Bacillus coagulans: purification and enzymatic properties.

Proline iminopeptidase [EC 3.4.11.5] was purified about 2,700-fold from cell-free extract of Bacillus coagulans by a series of column chromatographies on DEAE-Toyopearl, PCMB-T-Sepharose, and hydroxyapatite, and gel filtration on Sephadex G-150. The purified enzyme was homogeneous as judged by disc gel electrophoresis. The enzyme was most active at pH 7.3 with Pro-beta-naphthylamide (Pro-2-NNap) as the substrate, and hydrolyzed Pro-X (X = amino acid including proline, peptide, amide, and arylamide) bonds when the proline residue was at the amino terminus. Pro-D-amino acid bonds were also susceptible to the enzyme. The enzyme was completely inhibited by p-chloromercuribenzoate (PCMB) and partially by proline but not by metal chelators, diisopropylphosphorofluoridate (DFP), or phenylmethanesulfonyl fluoride (PMSF). The enzyme inactivated with PCMB was reactivated by incubation with 2-mercaptoethanol. These results and the chromatographic profile on PCMB-T-Sepharose suggest that the enzyme is a sulfhydryl enzyme. The isoelectric point of the enzyme was 4.0, and the molecular weight of the enzyme was estimated to be 40,000 by gel filtration on Sephadex G-100 and 35,000 by sodium dodecyl sulfate (SDS) gel electrophoresis, indicating that the enzyme exists as a monomer.

Factors that influence acyl proline cleavage by sodium in liquid ammonia.

The reductive cleavage of aminoacyl proline bonds by sodium in liquid ammonia was compared by a simple chromatographic technic for various protected and unprotected analogs of the C‐terminal tetrapeptide of the insulin B‐chain, ‐Thr‐Pro‐Lys‐Ala‐OH. The literature suggests that the Thr‐Pro bond in this peptide is especially sensitive to Na‐NN 3, compared to various other acyl proline bonds. The present study shows that this is true regardless of whether the sidechains, the α‐amino, and the α‐carboxyl groups are protected or free when they are introduced into liquid ammonia; there is no difference in the amount of reductive Thr‐Pro cleavage despite the different numbers of protons released into liquid ammonia by the functional groups of the residues surrounding the Thr‐Pro bond. The C‐terminal tetrapeptide and its blocked derivatives, prepared by solid phase synthesis, were reduced by Na‐NH 3 to the same extent as similarly synthesized B‐chains and natural B‐chain. Thr‐Pro cleavage could be minimized by sharply limiting the amount of sodium and the time of exposure of the peptide to it. The results are therefore useful in planning synthetic approaches to the B‐chain.The Ser‐Pro bond shares the lability of the Thr‐Pro bond to Na‐NH 3 reduction, whereas the Val‐Pro bond is only half as labile.

The Tryptic Digestion of S-Aminoethylated Ribonuclease

Abstract The peptides produced by the tryptic digestion of S-aminoethylated bovine pancreatic ribonuclease support the generally accepted amino acid sequence for this enzyme and also demonstrate the usefulness as well as some special limitations of the aminoethylation procedure. The relative extents of hydrolysis at different peptide bonds were estimated from the yields of purified peptides. Under the conditions used here for tryptic hydrolysis the approximate cleavage of arginyl and lysyl bonds was estimated at 83%, while the corresponding cleavage of aminoethylcysteinyl bonds averaged 56%. Exceptions to these generalizations included the very limited cleavage of lysyl and aminoethylcysteinyl bonds which were adjacent to other basic amino acid residues, and, of course, the negligible splitting of the lysyl proline bond and the amino-terminal lysyl glutamic acid bond. The extent of cleavage at aminoethylcysteinyl bonds appeared to show greater variability than that at lysyl and arginyl bonds.

CLEAVAGE OF PEPTIDE PROLINE BONDS BY LITHIUM ALUMINUM HYDRIDE.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTClevage of Peptide Proline Bonds by Lithium Aluminum Hydride*Michael A. Ruttenberg, Te Piao King, and Lyman C. CraigCite this: Biochemistry 1964, 3, 6, 758–764Publication Date (Print):June 1, 1964Publication History Published online1 May 2002Published inissue 1 June 1964https://doi.org/10.1021/bi00894a004RIGHTS & PERMISSIONSArticle Views184Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (799 KB) Get e-Alerts Get e-Alerts