Peptide Leucine Research Articles

Peptidase mutants of Salmonella typhimurium.

Six peptidase activities have been distinguished electrophoretically in cell extracts of Salmonella typhimurium with the aid of a histochemical stain. The activities can also be partially separated by chromatography on diethylaminoethyl-cellulose. These peptidases show overlapping substrate specificities. Mutants (pepN) of the parent strain leu-485 lacking one of these enzymes (peptidase N) were obtained by screening for colonies that do not hydrolyze the chromogenic substrate l-alanyl-beta-naphthylamide. The absence of this broad-specificity peptidase in leu-485 pepN(-) mutants allowed the selection of mutants unable to use l-leucyl-l-alaninamide as a leucine source. These mutants (leu-485 pepN(-)pepA(-)) lack a broad-specificity peptidase (peptidase A) similar to aminopeptidase I previously described in Escherichia coli. Mutants (pepD) lacking a dipeptidase (peptidase D) have been isolated from a leu-485 pepN(-)pepA(-) parent by penicillin selection for mutants unable to use l-leucyl-l-glycine as a leucine source. Mutants (pepB) lacking a fourth peptidase (peptidase B) have been isolated from a leu-485 pepN(-)pepA(-)pepD(-) strain by penicillin selection for failure to utilize l-leucyl-l-leucine as a source of leucine. Single recombinants were obtained by transduction for each of the peptidases missing in a leu-485 pepN(-)pepA(-)pepD(-)pepB(-) strain. The growth response of these recombinants to leucine peptides shows that all of these peptidases can function in the catabolism of peptides and that they display overlapping substrate specificities in vivo.

Carbon 13 Nuclear Magnetic Resonance of Pentapeptides of Glycine Containing Central Residues of Aliphatic Amino Acids

Abstract Pentapeptides containing either glycine, l-alanine, l-valine, l-leucine, or l-isoleucine as central residue in the pattern glycylglycyl-X-glycylglycine have been studied by proton-decoupled natural abundance 13C Fourier transform nuclear magnetic resonance spectroscopy. Resonances were assigned by comparison with the free amino acids and by detailed observation of changes in chemical shifts with pH over the range 1.32 to 10.43. The effect of varying the central residue on the chemical shifts of the flanking glycine residues was established. Small effects ascribable to incipient aggregation were noted, both in terms of chemical shifts and relaxation properties. Each resonance was categorized according to the degree of sensitivity to the state of protonation of the terminal groups, and the pK values at 26° for those groups were determined from the pH dependence of the most sensitive resonances. The sensitive terminal resonances undergo broadening which is maximum near the pK. Spin-lattice relaxation times, T1, of protonated carbon nuclei were measured at two or more pH values in all cases except for the glycine pentapeptide. For each peptide Cα resonances showed gradients in increasing T1 to each side from the central residue, indicative of contributions from segmental motion and internal rotation along the backbone in addition to the over-all rotational motion of the molecule. Internal rotational modes are expressed as well in the aliphatic side chains, especially by the most peripheral methyl groups for which spinning around the attaching bond is clearly prominent. Comparison of the anionic and cationic forms of the alanine, valine, and leucine peptides indicates that the rate of internal rotation of Cα of the NH2-terminal glycine residues increases with deprotonation of the ammonium group.

A study of some glycine and leucine peptide complexes of copper, nickel, and zinc.

A study of some glycine and leucine peptide complexes of copper, nickel, and zinc.

Optical rotatory dispersion. LII. Tri- and tetra-peptides of leucine and their protected derivatives.

The optical rotatory dispersion curves of all the diastereoisomeric tri- and tetra-peptides of leucine have been measured in water, acid, and alkali; protected derivatives of the tri- and tetra-peptides have also been examined in methanol. The results are closely similar to those reported earlier for alanine peptides and suggest that, for each possible diastereoisomer, the alanine and leucine peptides have the same conformation in solution, with respect to the peptide chain and its immediate substituents.

Immunochemistry of Synthetic Polypeptides and Polypeptidyl Proteins

Summary Quantitative precipitation studies of the antibodies produced in response to the immunization of rabbits immunized with bovine albumin modified by the addition of peptides of glutamic acid, lysine, leucine, or phenylalanine indicated that some of the antibodies were specific for the carrier protein, others were specific for the added polypeptide, and that some require both the modification and at least a part of the carrier protein. Similar quantitative studies on the sera prepared against rabbit albumin which had been modified in the same manner indicated that there were antibodies toward the added polypeptide and possibly some which required a portion of the carrier protein and the modification. The possible explanations for the existence of the antibodies requiring the modification and at least part of the carrier protein are discussed. Absorption experiments on antisera to the modified bovine albumins indicate that similarly modified rabbit albumins precipitate all the antibodies produced in response to the added polypeptide, but that unmodified bovine albumin does not precipitate all of the antibodies and that it may form a nonprecipitating complex with some antibodies which prevents subsequent precipitation with the homologous antigen. The modification of the bovine albumin with various polypeptides was found to weaken the antigenicity of the protein. The length of the added polypeptide chain appears to be more important in the change of specificity than the number of added polypeptide chains.

Chemical stability and metabolic utilization of asparagine peptides

l-Leucyl- l-asparagine and l-asparaginyl- l-leucine are utilized as well as l-asparaginylglycine and glycyl- l-asparagine by Leuc. mesenteroides. The growth response to these peptides approximates that to l-aspartic acid and is far superior to that to l-asparagine. l-Aspartylglycine and glycyl- l-aspartic acid at high concentrations are superior to l-aspartic acid as a source of the dicarboxylic acid. The glycine peptides serve as better sources of glycine than glycine itself. The growth response to the leucine peptides is equal to that to leucine. Cell-free extracts of Leuc. mesenteroides show strong asparaginase activity. Observations on the enzymatic splitting of the asparagine peptides suggest that the peptides are cleaved into the amide and glycine or leucine and that the free amide is deamidated. It appears that the superior utilization of asparagine peptides when compared with that of asparagine is the result of the inability of the latter to reach the sites of its metabolism by the bacterial cell. Procedures for the syntheses of leucylasparagine, asparaginylleucine, α-aspartylglycine and glycylaspartic acid are described. The instability of glycylasparagine in acid and of asparaginylglycine in alkali is demonstrated and discussed.

Specificity of Gathepsin III

Summary1. A purified cathepsin III (leucine aminopeptidase) preparation hydro-lyzed L-leucinamide from 2 to 3 times as fast as either L-leucylglycine or L-leucyl-γ-amino-butyric acid and about 4 times as fast as L-leucyl-β-alanine. The activity of the enzyme was not affected by the proximity to the peptide bond of the free carboxyl group of leucyl peptides. 2. The fact that L-leucinamide is hydrolyzed faster than are the peptides of leucine can possibly be explained by the hypothesis that the large groups attached to the peptide nitrogen of the substrates interfere with the formation of an enzyme-substrate complex. 3. The hydrolysis of the substrates by enzyme preparation A closely approximated zero order kinetics. The failure to observe a regular kinetic order for the reactions catalyzed by preparations B and C may be the result of destruction of the enzyme in the more highly purified preparations.

Infrared Spectra and the Structure of Glycine and Leucine Peptides1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared Spectra and the Structure of Glycine and Leucine Peptides1Elkan R. Blout and Seymour G. LinsleyCite this: J. Am. Chem. Soc. 1952, 74, 8, 1946–1951Publication Date (Print):April 1, 1952Publication History Published online1 May 2002Published inissue 1 April 1952https://doi.org/10.1021/ja01128a023RIGHTS & PERMISSIONSArticle Views686Altmetric-Citations49LEARN 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 (742 KB) Get e-Alerts Get e-Alerts

The unit-cell dimensions and the space groups of some simple peptides of glycine, alanine and leucine

The unit-cell dimensions and the space groups of some simple peptides of glycine, alanine and leucine

INHIBITION OF BACTERIAL GROWTH BY LEUCINE PEPTIDES

INHIBITION OF BACTERIAL GROWTH BY LEUCINE PEPTIDES