Protein partial hydrolysis, chemical

The hydrolysis of proteins by chemical and enzymatic methods is discussed by R. L. Hill in the second chapter. The chapter should serve as a standard source for information on the many operational techniques with which only the experienced specialist is likely to be familiar. Dr. Hill covers not only the partial hydrolysis of proteins by general and specific procedures but also tbe total enzymatic hydrolysis of proteins for the purpose of amino acid analysis. 

Peptide cleavage, partial hydrolysis of peptides and proteins by chemical ( end group analysis) or enzymatic methods (-> proteolysis) for sequence analysis. Limited peptide cleavage (limited proteolysis) is important for various metabolic processes. 

Similarly, naturally derived surfactants extracted from fermentation broths or prepared by partial hydrolysis of natural extracts can contain polysaccharides, proteins, and phospholipids. For example, rhamnolipids and sophorolipids have unique structural features that cause them to deposit on chemically similar surfaces and modify surface energy even at very low concentrations. Clearly, the emergence of biotechnology in the twenty-first century will drive the development of new surfactants from microbial fermentation, and improve the commercial viability of known surfactants from such processes. 

Mixtures of peptides result from partial degradation of proteins. Separation of the individual components and establishment of their amino acid sequence form the basis for elucidating the chemical structure of proteins for information about the methods of degradation which yield larger and smaller peptides, reference may be made to Sanger [130] (partial hydrolysis) Craig et al. (oxidative fission of S—S... 

Ando, T., Iwai, K., Ishii, S., Yamasaki, M., Kimura, M., Tobita, T., Sato, M., Abuku-MAGAWA, E. Chemical structure of protamines — Studies by partial hydrolysis (in Japanese). Proc. 7th Symposium on Protein Structure, Tokyo, Nov. 4, pp. 11—12, 1955. 

Watanabe and Arai wrote an excellent review on the properties of enzymatically modified proteins and compared the chemical and enzymatic processes of various proteins [135]. Enzymatic processes can normally be carried out under milder and therefore safer experimental conditions than conventional chemical processes. Proteolytic enzymes have been used on proteins to improve their solubility soy protein, leaf protein concentrates, fish protein concentrates, meat proteins, egg proteins, milk proteins, and blood proteins. Special attention was given to caseins, gelatins, egg proteins, and cereals. Partial hydrolysis of these proteins under well-controlled conditions can produce emulsifying and whipping agents... 

See Section IV.1 for alternative methods of chiral resolution. Partial chemical hydrolysis of proteins and peptides with hot 6 M HC1, followed by enzymatic hydrolysis with pronase, leucine aminopeptidase and peptidyl D-amino acid hydrolase, avoids racemiza-tion of the amino acids281. The problems arising from optical rotation measurements of chiral purity were reviewed. Important considerations are the nonideal dependence of optical rotation on concentration and the effect of chiral impurities282. 

An excellent review on protein hydrolysis for amino acid composition analysis has been published by Eountoulakis and Lahm [190], Hydrolysis can be performed by either chemical (under either acidic or basic conditions) or enzymatic means. The acidic hydrolysis itself can be carried out in a liquid or a gas-phase mode. The conventional acid hydrolysis uses 6M HCl for 20-24 h at 110°C under vacuum [200], In these conditions, asparagine and glutamine are completely hydrolyzed to aspartic acid and glutamic acid, respectively. Tryptophan is completely destroyed (particularly in the presence of high concentrations of carbohydrate), while cysteine and sometimes methionine are partially oxidized. Tyrosine, serine, and threonine are partially destroyed or hydrolyzed and correction factors have to be applied for precise quantification [190,201],... 

Zinc efflux is mediated by a zinc exporter known as ZntA (Zn + transport or tolerance), a membrane protein which was identified through studies of bacterial strains that were hypersensitive to zinc and cadmium. Sequence inspection revealed that ZntA was a member of the family of cation transport P-type ATPases, a major family of ion-translocating membrane proteins in which ATPase activity in one portion of the protein is used to phophorylate an aspartate within a highly conserved amino acid sequence, DKTG, in another portion of the protein. The cysteine rich N-terminus of these soft metal transport proteins contains several metal-binding sites. How the chemical energy released by ATP hydrolysis results in metal ion transport is not yet known, in part because there is only partial information about the structures of these proteins. The bacterial zinc exporter also pumps cadmium and lead and is therefore also involved in protection from heavy metal toxicity (see Metal Ion Toxicity). 

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