Carboxypeptidase, activity during

This is thought to be achieved by the inhibition of transpeptidase and DD-carboxypeptidase activity during the final stages of murein formation... 

During last decades the domains C-2 symmetry (the dyad rotation symmetry) of low-B palindrome was established in many enzymes (chymotrypsin, trypsin, aspartyl proteinases, HIV-1 protease, carboxypeptidase A, phospholipase A-2 ribonuclease, etc.) (Lumry, 2002 and references therein). It is proposed that the pair domain closure causes constrain of pretransition state complex that activates cleavage or formation of chemical bonds. Thus control of strong bonds by the cooperation of many matrix or knots bonds takes place. As an example, in the active site of carboxypeptidase A the zinc ion is attached to one of the catalytic domains by histidine 69 and glutamine 72 and connected by hystidine 196 to the second domain. Similar structures were found in the chymotrypsin and pepsin active sites where protons are driven under compression of the domains closure. 

The application of the non-urethane PhAc blocking group results in ca. 6% racemization during the construction of the phenylacetamido-protected dipeptides by chemical activation of the phenylacetamido amino acids. This disadvantage can be overcome by forming the peptide bonds enzymatically, e.g. with trypsin [26,27], chymotrypsin [26,28], or carboxypeptidase Y [26,29]. An interesting example is the biocatalyzed synthesis of leucine-enkephalin tert-butyl ester [25e], in which phenylacetamides are introduced and cleaved by means of penicillin G acylase, and the elongation of the peptide chain is carried out with papain or a-chymotrypsin. 

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