Carboxypeptidase primary structure

Renaturation of denatured protein is dictated by the primary structure of the protein. The trypsin family of enzymes and carboxypeptidase A are synthesized as proenzymes that are proteolytically activated. The proteolyzed, active enzymes have primary structures different from the gene product and are not active upon renaturation. In addition, zinc is a cofactor required for carboxypeptidase A activity. 

Chymotrypsinogen, a single polypeptide chain of 245 amino acid residues, is converted to a-chymotrypsin, which has three polypeptide chains linked by two of the five disulfide bonds present in the primary structure of chymotrypsinogen. tt- and S-chymotrypsin also have proteolytic activity. In contrast, the conversion of procarboxypeptidase to carboxypeptidase involves the hydrolytic removal of a single amino acid. 

W. Gebhard, M. Schube, and M. Eulitz. cDNA cloning and complete primary structure of the small, active subunit of human carboxypeptidase N. Eur. J. Biochem. 778 603-607 (1989). 

Homandberg, G. A., Litwiller, R. D. and Peanasky, R. J. (1989) Carboxypeptidase inhibitors from Ascaris suum the primary structure. Arch. Biochem. Biophys. 270 153-161. 

The primary structure of a protein is the sequence of its amino acids and the location of all its disulfide bridges. The N-terminal amino acid of a peptide or protein can be determined with Edman s reagent. The C-terminal amino acid can be identified with carboxypeptidase. Partial hydrolysis hydrolyzes only some of the peptide bonds. An exopeptidase catalyzes the hydrolysis of a peptide bond at the end of a peptide chain. An endopeptidase catalyzes the hydrolysis of a peptide bond that is not at the end of a peptide chain. 

Carboxypeptidases (CP), single-chain exo-peptidases that remove successive amino acids from the C-terminal end of peptides and proteins. CPs are highly specific for the side-chain moieties of the amino acids to be cleaved, and are classified into various groups and families. The CP approach is used for the end group analysis in primary structure determination. Normally,... 

The primary structure of a protein is the sequence of its amino acids and the location of all its disulfide bridges. The N-terminal amino acid can be determined with Edman s reagent. The C-terminal amino acid can be identified with a carboxypeptidase. 

In bovine pancreatic carboxypeptidase A, Zn is bound to the enzyme at its active site by forming a complex with His 69, Glu 72, and His 196, as well as with a water molecule. (Glu 72 means that, starting from the N-terminal end of the enzyme, Glu is the seventy-second amino acid.) It is common to specify the source of the enzyme because, although carboxypeptidase As from different sources employ the same mechanism, they have slightly different primary structures. 

The shape of a large protein is influenced by many factors including of course Its primary and secondary structure The disulfide bond shown m Figure 27 18 links Cys 138 of carboxypeptidase A to Cys 161 and contributes to the tertiary structure Car boxypeptidase A contains a Zn " ion which is essential to the catalytic activity of the enzyme and its presence influences the tertiary structure The Zn ion lies near the cen ter of the enzyme where it is coordinated to the imidazole nitrogens of two histidine residues (His 69 His 196) and to the carboxylate side chain of Glu 72... 

Carboxypeptidase A"" (CPA, EC 3.4.17.1) is a proteolytic enzyme that cleaves C-terminal amino acid residues with hydrophobic side chains selectively. Several X-ray structures are available" The active site of CPA consists of a hydrophobic pocket (primary substrate recognition site) that is primarily responsible for the substrate specificity, a guanidinium moiety of Argl45 that forms hydrogen bonds to the carboxylate of the substrate, and Glu270, whose carboxylate plays a critical role, functioning either as a nucleophile to attack the scissUe carboxamide carbonyl carbon of the substrate or as a base to activate the zinc-bound water molecule, which in turn attacks the scissile peptide bond ". However, semiempirical calculations had shown that the direct attack of... 

The interactions of 8-lactams with PBPs indicate that these compounds are structural analogues of R-D-alanyl-D-alanine, the natural substrate of peptidoglycan transpeptidases and D-alanine carboxypeptidases, where R is the remainder of the pentapeptide. The mechanisms of the transpeptidase and carboxypeptidase reactions are thought to involve formation of an acyl-enzyme intermediate that can react with either a primary amine (e.g., an a-amino group) to form a peptide bond, or with water to form a carboxylic acid. In both reactions D-alanine is released before the acyl enzyme is formed. When a S-lactam antibiotic enters the binding site, the /1-lactam bond is hydrolyzed, and the resulting acyl group reacts with the active-site... 

The shape of a large protein is influenced by many factors, including, of course, its primary and secondary structure. The disulfide bond shown in Figure 27.18 links Cys-138 of carboxypeptidase A to Cys-161 and contributes to the tertiary structure. Car-... 

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