Acidic tripeptides

Proteins are frequently referred to as polypeptides. Of course, we have dipeptides (two amino acids), tripeptides (three amino acids), oligopeptides (a few amino acids), and so forth. A typical dipeptide is Ala-Val ... 

Re-formation of the Taste of BMP. According to the above results, the taste of BMP might produced by the combination of the basic amino acid (Lys) at N-terminal and acidic amino acids at the middle part. To confrnn this idea, we prepared a mixed solution of the N-terminal dipeptide (Lys-Gly), the acidic tripeptide at the middle part (Asp-Glu-Glu) and C-terminal tripeptide (Ser-Leu-Ala) and examined the taste. We also studied tastes of a mixture in which a basic dipeptide fragment was replaced by Orn-p-Ala, a salty dipeptide, and a mixture in which Glu-Glu replaced an acidic tripeptide fragment. The result are shown in Table XIV. All of the combinations produced the same character of the taste as BMP. It means that the taste of BMP is mainly produced by the combined effect of the N-terminus basic dipeptide and the acidic tripeptide of the middle part. However, taste strength of the mixture became... 

Tab. 4.6 Capped amino acids, tripeptides, and hexapeptides and their physicochemical properties. (Adapted from Tab. 2 of ref. 38)...

The arrows point to the two amide or peptide links. Note that in this example, one of the amino acid residues (aspartic acid) has an extra carboxylic acid group in the side chain or R group. As a result, the molecule above is called an acidic tripeptide because it contains more carboxyl groups than amines. 

Verbruggen, C., De Craecker, S.. Rajan, P, Jiao, X.-Y, Borloo, M., Smith, K., Fairlamb, A.H., and Haerners, A., Phosphonic acid and phosphinic acid tripeptides as inhibitors of glutathionylspermidine synthetase, Bioorg. Med. Chem. Lett., 6, 253, 1996. 

Proteins are amino acids linked tfirough peptide bonds. Dipeptides fiave two amino acids, tripeptides fiave tfiree amino acids, and so on. Digestive proteases are enzymes tfiat cleave the peptide bonds between the amino acids (see Chap.1, Fig. 1.5). 

Peptides are formed from two or several amino acids linked by acid amide bonds. Coupling of two amino acids yields dipeptides, of three amino acids tripeptides, etc. Oligopeptides contain up to 10 amino acids, polypeptides 10 to about 100 amino acids. The sequence of amino acids in a peptide is called its primary structure. 

The following short descriptions of the steps involved in the synthesis of a tripeptide will demonstrate the complexity of the problem amino acid units. In the later parts of this section we shall describe actual syntheses of well defined oligopeptides by linear elongation reactions and of less well defined polypeptides by fragment condensation. 

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" ... 

Tripeptide (Section 27 1) A compound m which three a ammo acids are linked by peptide bonds... 

The sequence of amino acids in a peptide can be written using the three-letter code shown in Figure 45.3 or a one-letter code, both in common use. For example, the tripeptide, ala.ala.phe, could be abbreviated further to AAF Although peptides and proteins have chain-like structures, they seldom produce a simple linear system rather, the chains fold and wrap around each other to give complex shapes. The chemical nature of the various amino acid side groups dictates the way in which the chains fold to arrive at a thermodynamically most-favored state. 

Fig. 11. Use of D-amino acids in the synthesis of a hairpin loop portion from the CD4 receptor (a) all L-Ser—Lys—Ala tripeptide constmcted in the natural...

Cysteine [52-90 ] is a thiol-bearing amino acid which is readily isolated from the hydrolysis of protein. There ate only small amounts of cysteine and its disulfide, cystine, in living tissue (7). Glutathione [70-18-8] contains a mercaptomethyl group, HSCH2, and is a commonly found tripeptide in plants and animals. Coenzyme A [85-61-0] is another naturally occurring thiol that plays a central role in the synthesis and degradation of fatty acids. 

Proteins. The most abundant and physiologically diverse natural biopolymers are proteins, which make up enzymes, hormones, and stmctural material such as hair, skin, and connective tissue. The monomer units of natural proteins, a-amino acids, condense to form dipeptides, tripeptides, polypeptides, and proteins. 

These signals in the NOE spectra therefore in principle make it possible to determine which fingerprint in the COSY spectrum comes from a residue adjacent to the one previously identified. For example, in the case of the lac-repressor fragment the specific Ser residue that was identified from the COSY spectrum was shown in the NOE spectrum to interact with a His residue, which in turn interacted with a Val residue. Comparison with the known amino acid sequence revealed that the tripeptide Ser-His-Val occurred only once, for residues 28-30. 

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

If you synthesized the tripeptide Leu-Phe-Ser from amino acids prepared by the Strecker synthesis, how many stereoisomers would you expect to be formed ... 

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. 

Given 20 different amino acids, a polypeptide chain of n residues can have any one of 20 possible sequence arrangements. To portray this, consider the number of tripeptides possible if there were only three different amino acids. A, B, and C (tripeptide = 3 =n ... 

FIGURE 10.10 The reaction of tridated sodium borohydride with the aspartyl phosphate at the active site of Na, K -ATPase. Acid hydrolysis of the enzyme following phosphorylation and sodium borohydride treatment yields a tripeptide containing serine, homoserine (derived from the aspartyl-phosphate), and lysine as shown. The site of phosphorylation is Asp" in the large cytoplasmic domain of the ATPase. 

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