Hydrolysis peptide, acid

TABLE 16.1 ACE inhibitory peptides derived from marine fish source, enzyme used for hydrolysis, amino acid sequence and IC50 value... 

Peptide thioesters (Section 15.1.10) are generally prepared by coupling protected amino acids or peptides with thiols and are used for enzymatic hydrolysis. Peptide dithioesters, used to study the structures of endothiopeptides (Section 15.1.11), may be prepared by the reaction of peptide nitriles with thiols followed by thiolysis (Pinner reaction). Peptide vinyl sulfones (Section 15.1.12), inhibitors of various cysteine proteases, are prepared from N-protected C-terminal aldehydes with sulfonylphosphonates. Peptide nitriles (Section 15.1.13) prepared by dehydration of peptide amides, acylation of a-amino nitriles, or the reaction of Mannich adducts with alkali cyanides, are relatively weak inhibitors of serine proteases. 

Hydrolysis. Peptide bonds of aspartic acid (Asp) residues are cleaved under dilute acidic conditions. Hydrolysis can take place at the N-terminal, the C-terminal, or both terminal peptide bonds adjacent to the Asp residue. 

Mulholland, M.R., Gobler, C.J., and Lee, C. (2002) Peptide hydrolysis, amino acid oxidation, and nitrogen uptake in communities seasonally dominated by Aureococcus anophagefferens. Lirnnol. Oceanogr. 47, 1094-1108. 

Alkaline hydrolysis of cockroach residues subsequent to extraction under nitrogen with 80% ethanol yielded methionine and methionine sulfoxide in a ratio of 10 to 1. Additional evidence for the presence of combined methionine sulfoxide was obtained by measuring the amount of methionine sulfoxide-S35 in acid and enzymatic hydrolyzates after assimilation of Na2S3504. The data are believed to be indicative of naturally occurring peptide- or polysaccharide -bound methionine sulfoxide. Other combined amino acids were determined by ion exchange chromatography of the 5% trichloroacetic acid-insoluble cockroach residues after hydrolysis with acid or alkali. /3-Alanine, normally present only in the soluble fraction of an organism, was found in the insoluble, proteinaceous residue. 

Based on the initial peptide sequencing yield divided by the estimated amount of protein digested which is based on hydrolysis/amino acid analysis of the submitted gel slice. 

Subsequently, the hydrolysis of acidic proteins occurs at pH 2-5 this is especially the case for peptides containing aspartate residues.3 Larger proteins are quite susceptible to this gastric proteolysis, while smaller peptides are unaffected by this mixture. 

Free hydroxyproline is measured in an aliquot of urine prior to hydrolysis total hydroxyproline is that amount present after complete hydrolysis (usually acid). The difference between the free and total measurements is bound or peptide hydroxyproline. 

The relative rate of hydrolysis in acid of any peptide bond and hence the yield of a given peptide is determined mainly by the number of hydrogen ions that can approach the bond. While the rate probably depends on a number of different factors, we may consider two which probably play a major role, namely, electrostatic effects and steric effects. 

Most of the acids obtained from proteins by hydrolysis with acids are optically active alkaline hydrolysis yields racemic forms. Fischer has prepared many optically active peptids, and has discovered that the configuration of the molecule is an important factor in its hydrolysis by trypsin. For example, d-alanyl-d-alanine is hydrolyzed, but d-alanyl-i-alanine is not. Racemic peptids, that is, those which consist of a mixture of equal parts of dextro and levo compounds, are hydrolyzed asymmetrically, only one form, and that the form which occurs in proteins, being attacked by the enzyme. Up to the present, only those peptids have been hydrolyzed which contain the optically active forms of the amino-acids which result from the hydrolysis of naturally occurring compounds. 

K-Casein was first isolated by Waugh and von Hippel (1956), who showed that this protein is responsible for the stability of the casein micelles and that its micelle-stabilizing properties are lost on renneting. Only /c-casein is hydrolyzed to a significant extent during the primary phase of rennet action. The primary cleavage site is Pheios-Metioe (Delfour et al, 1965), which is many times more susceptible to hydrolysis by acid proteinases (all commercial rennets are acid proteinases) than any other peptide bond in the milk protein system. 

Peptide hydrolysis, complete hydrolysis of peptides and proteins for amino acid analysis or the production of individual amino acids from the peptide or protein hydrolysate. For this purpose, numerous chemical and enzymatic protocols are known, but none of these procedures alone is fully satisfactory. Besides hydrolysis with 6 M hydrochloric acid at 120 °C for 12 h, or with dilute alkali (2-4 M NaOH) at 100 °C for 4-8 h, mixtures of peptidases can also be used for complete peptide hydrolysis. Restricted or limited peptide hydrolysis ( peptide cleavage) is important for - sequence analysis and peptide mapping. 

The precise quantification of the amount of peptide synthesized is determined through amino acid analysis by HPLC after peptide hydrolysis in acid medium considering those acid-resistant amino acids. Although amino acid analysis is usually performed after cleavage from the resin, it can also be conducted to the peptide... 

On hydrolysis with acids phalloidin yields L-alanine, 4-cis-L-hydroxyproline, D-threonine, L-y, -dihydroxyleucine, L-cysteine and j8-oxindolalanine ( oxytryptophan ). The tryptophan derivative is not a genuine building component of the cyclic peptides it is formed by hydrolysis of a thioether crosslink between position 2 of tryptophan and the side chain of cysteine (tryptathionine). The structure of the bicyclic heptapeptide is shown in Fig. 21. 

In general, abiotic substitution reactions proceed slowly, but can be greatly accelerated by enzymes. Enzyme-mediated substitutions frequently involve cysteine residues in proteins or peptides, such as glutathione. Biotic and abiotic hydrolysis of halogenated aliphatic compounds yields alcohols by hydros l substitution at the halogenated carbon [10]. If these alcohols are themselves halogenated, further hydrolysis to acids or diols can occur. Examples of microbially-mediated hydrolysis reactions, together with responsible enzymes, are provided in Table 1. 

Peptide bond hydrolysis Aspartic acid residues and others... 

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