Peptides dipeptides

Know the meaning of peptide bond, peptide, dipeptide, tripeptide, and so on N-terminal and C-terminal amino acid cysteine unit disulfide bond. 

Numerous ESR studies of the photodamage effect on biologically important molecules have been reported in recent years. Brustad (377) studied the UV-irradiation of the enzyme trypsin and found a linear correlation of the loss of enzyme activity with concentrations of the photoproduced radical. Leterrier and Douzou (378) have applied ESR techniques to study the mechanism of the photoreduction of flabin mononucleotide. A number of investigations deal with photodamage of aliphatic amino acids, glycine peptides, dipeptides, and alanine peptides (379-383). John et al. 

The names and the structure of the a-amino acids present in proteins are shown in Table 12.1.1. Besides the amino acids that are protein constituents, many other amino acids occur naturally in living systems. Amino acids are linked in proteins through an amide bond (or peptide bond) formed between the amino group of one amino acid and the carboxyl group of the other amino acid. The peptide bond contains the planar group of atoms CaNCC. When a small number of amino acids are linked through F>eptide bonds they form simple peptides (dipeptides, tripeptides, etc.). Long chains of amino acids are commonly named polypeptides. The sequence of amino acids in a polypeptide is known as primary structure. A polypeptide chain can be described schematically as follows ... 

Aliphatic and aromatic amines, alkaloids, amino adds, amino sugars, carboxylic and sul-fanfiic adds, drugs, indole derivatives, nucleobases, nucleosides, nucleotides, peptides, dipeptides, polypeptides, phenols, phenothiazine bases, steroids, sulfonamides, water-soluble food dyes... 

Waugh, R. L. Bowie, J. H. Collision induced dissociations of deprotonated peptides Dipeptides containing phenylalanine, tyrosine, histidine, and tryptophan. Int. J. Mass Spectrom. Ion Process. 1991, 107, 333. 

Prolyl aminopeptidases (PAP) are exopeptidases that hydrolytically cleave off an N-terminal Pro from peptides. The enzymes belong to the a/p hydrolase fold proteins. A PAP from Streptomyces thermoluteus carrying the active site nucleophile mutation S144C was used as a catalyst for the synthesis of proline-containing peptides. Dipeptide synthesis was obtained with an amino acid methyl or benzyl ester as the acyl donor and prolyl-OBz as the nucleophile [21]. Under alkaline conditions, cycli-zation and polymerization of prolyl-OBz was observed. 

A dipeptide is a molecule consisting of two ammo acids joined by a peptide bond A tnpeptide has three ammo acids joined by two peptide bonds a tetrapeptide has four ammo acids and so on Peptides with more than 30-50 ammo acids are polypeptides Proteins are polypeptides that have some biological function... 

A key biochemical reaction of ammo acids is their conversion to peptides polypeptides and proteins In all these substances ammo acids are linked together by amide bonds The amide bond between the ammo group of one ammo acid and the carboxyl of another IS called a peptide bond Alanylglycme is a representative dipeptide... 

There are several levels of pepfide sfrucfure The primary structure is the ammo acid sequence plus any disulfide links With the 20 ammo acids of Table 27 1 as building blocks 20 dipeptides 20 tripeptides 20" tetrapeptides and so on are possible Given a peptide of unknown structure how do we determine its ammo acid sequence" ... 

Higher peptides are prepared m an analogous way by a direct extension of the logic just outlined for the synthesis of dipeptides... 

Peptide is the name assigned to short polymers of amino acids. Peptides are classified by the number of amino acid units in the chain. Each unit is called an amino acid residue, the word residue denoting what is left after the release of HgO when an amino acid forms a peptide link upon joining the peptide chain. Dipeptides have two amino acid residues, tripeptides have three, tetrapeptides four, and so on. After about 12 residues, this terminology becomes cumbersome, so peptide chains of more than 12 and less than about 20 amino acid residues are usually referred to as oligopeptides, and, when the chain exceeds several dozen amino acids in length, the term polypeptide is used. The distinctions in this terminology are not precise. 

Describe the synthesis of the dipeptide Lys-Ala by Merrifield s solid phase chemical method of peptide synthesis. What pitfalls might be encountered if yon attempted to add a leucine residue to Lys-Ala to make a tripeptide ... 

It has been shown that glyeine amides of aminobenzophenones are readily converted to the corresponding benzodiazepines in vivo. Peptides which terminate in such a moiety should thus serve as a benzodiazepine prodrug after hydrolysis by peptidases. One of the glycine residues in lorzafone (194)is presumably removed metabolicaUy in this manner to give a benzodiazepine precursor which spontaneously cyclizes. Acylation of benzophenone 190 with the trityl protected dipeptide 191, as its acid chloride 192, affords the amide 193. Removal of the trityl protecting group with acid yields lorzafone (194) [50]. 

Proteins and peptides are amino acid polymers in which the individual amino acids, called residues, are linked together by amide bonds, or peptide bonds. An amino group from one residue forms an amide bond with the carboxyl of a second residue, the amino group of the second forms an amide bond with the carboxyl of a third, and so on. For example, alanylserine is the dipeptide that... 

The incretin effect is reduced in type 2 diabetes, and this is attributed, at least in part, to reduced secretion of GLP-1. The biological actions of GLP-1 remain essentially intact in type 2 diabetes, but administration of extra GLP-1 is not a practical therapeutic option because the peptide is degraded rapidly if A < 2 min) by the enzyme dipeptidyl peptidase IV (DPP-4). DPP-4 cleaves the N-terminal dipeptide from many of the peptides that have either an alanine or a proline residue penultimate to the N-terminus (Fig. 6). 

An exopeptidase that sequentially releases a dipeptide from the N-terminus of a protein or peptide. Dipeptidy 1-peptidases are included in Enzyme Nomenclature subsubclass 3.4.14 along with tripeptidyl-peptidases. 

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