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Carboxypeptidase Conformational

Chymotrypsin, 170,171, 172, 173 Classical partition functions, 42,44,77 Classical trajectories, 78, 81 Cobalt, as cofactor for carboxypeptidase A, 204-205. See also Enzyme cofactors Condensed-phase reactions, 42-46, 215 Configuration interaction treatment, 14,30 Conformational analysis, 111-117,209 Conjugated gradient methods, 115-116. See also Energy minimization methods Consistent force field approach, 113 Coulomb integrals, 16, 27 Coulomb interactions, in macromolecules, 109, 123-126... [Pg.230]

Endoproteinase LysC cleaved AP-A between Lys37 and Ala38 to yield a derivative with cardiotonic activity an order of magnitude lower than that of the parent molecule (Monks SA and Norton RS, unpublished results). This reduction in activity could be a consequence of local conformational perturbations. Treatment of AP-B with carboxypeptidase removed Lys49, resulting in only a two-fold reduction in cardiotonic activity (Monks SA and Norton RS, unpublished results). [Pg.306]

Figure 23 The conformational changes induced in carboxypeptidase on binding of the pseudosubstrate glycyltyrosine... Figure 23 The conformational changes induced in carboxypeptidase on binding of the pseudosubstrate glycyltyrosine...
Although many of these general features are correct, these mechanistic conclusions are based upon the assumption that the properties of the enzyme in solution are conserved on crystallization. It appears from Raman studies on arsanilazotyrosine-248 carboxypeptidase that the enzyme exists in solution in a number of different forms.509 It is not certain that the form which crystallizes out is the kinetically active species. Indeed there is evidence that the kinetics of carboxypeptidase in solution differ from those of the enzyme crystals, with the crystalline enzyme being 1000-fold less active with some substrates.510 The interaction of Gly-L-tyr with Mn carboxypeptidase A, studied by 1H NMR techniques, does not involve coordination of the carboxyl group of the substrate, and may well represent a different conformation from the one studied by crystallographic techniques.511 Several conformational forms of the Cd11 carboxypeptidase A have been found in solution, while the enzyme exists in a different form in the crystal state.312... [Pg.604]

The specificities of the various digestive exo- and endopep-tidases suggest that they act synergistically to fulfill a major nutritional function. The concerted action of trypsin, chy-motrypsin, pepsin, and carboxypeptidases A and B facilitate and ensure formation of essential amino acids. The chemical characteristics and metalloenzyme nature of two bovine exopeptidases, lens aminopeptidase and pancreatic carboxy-peptidase A, indicate similarities in their mechanisms of action. However, the aminopeptidase exhibits an unusual type of metal ion activation not observed unth carboxy-peptidase. Chemical and physicochemical studies reveal that the latter enzyme has different structural conformations in its crystal and solution states. Moreover, various kinetic data indicate that its mode of action toward ester substrates differs from that toward peptide substrates. The active site metal atom of carboxypeptidase figures prominently in these differences. [Pg.220]

It is unlikely that the introduction of the probe itself induces these changes in protein conformation since recent studies with nitrocarboxy-peptidase (64) confirm the findings of Johansen and Vallee (62, 63). Treatment of carboxypeptidase crystals with tetranitromethane exclusively nitrates tyrosine-248. In solution nitrocarboxypeptidase exhibits a visible absorption band with a maximum at 428 nm titrating with a pK of about 6.3. This abnormally low pK value (relative to model nitro-... [Pg.234]

Such data suggests that a re-evaluation of current views on the structural features of carboxypeptidase catalysis is necessary. Moreover these data question whether analogous conformational differences between... [Pg.236]

Zinc usually binds to proteins via residues of cysteine and histidine. Sometimes zinc is bound to residues of glutamate or aspartate. The zinc ion sometimes plays a catalytic role and sornetimes a structural role. In the latter case, it helps maintain the three-dimensional structure or conformation of the protein. For example carboxypeptidase A contains twr> atoms of zinc. One is required for catalytic activity and is bound to cysteine and histidine. The other, which plays a structural role, is bound only hr cysteine. Cytoplasmic supeioxide dismutase is a dimer, ft contains one atom of Cu and one of Zn + per subunit. The zinc is bound via three residues of histidine and one residue of aspartate. It is buried deep within the enzyme and serves a structural role. The copper atom is bound via four residues of histidine. It resides dose to the surface of the protein and participates in the chemistry of catalysis. [Pg.805]


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