Primary Citation of Related Structures: 1UOO, 1UOP, 1UOQ
PubMed Abstract:
The positive electrostatic environment of the active site of prolyl oligopeptidase was investigated by using substrates with glutamic acid at positions P2, P3, P4, and P5, respectively. The different substrates gave various pH rate profiles. The pKa values extracted from the curves are apparent parameters, presumably affected by the nearby charged residues, and do not reflect the ionization of a simple catalytic histidine as found in the classic serine peptidases like chymotrypsin and subtilisin ...
The positive electrostatic environment of the active site of prolyl oligopeptidase was investigated by using substrates with glutamic acid at positions P2, P3, P4, and P5, respectively. The different substrates gave various pH rate profiles. The pKa values extracted from the curves are apparent parameters, presumably affected by the nearby charged residues, and do not reflect the ionization of a simple catalytic histidine as found in the classic serine peptidases like chymotrypsin and subtilisin. The temperature dependence of kcat/Km did not produce linear Arrhenius plots, indicating different changes in the individual rate constants with the increase in temperature. This rendered it possible to calculate these constants, i.e. the formation (k1) and decomposition (k-1) of the enzyme-substrate complex and the acylation constant (k2), as well as the corresponding activation energies. The results have revealed the relationship between the complex Michaelis parameters and the individual rate constants. Structure determination of the enzyme-substrate complexes has shown that the different substrates display a uniform binding mode. None of the glutamic acids interacts with a charged group. We conclude that the specific rate constant is controlled by k1 rather than k2 and that the charged residues from the substrate and the enzyme can markedly affect the formation but not the structure of the enzyme-substrate complexes.
Related Citations:
Electrostatic Effects and Binding Determinants in the Catalysis of Prolyl Oligopeptidase: Site Specific Mutagenesis at the Oxyanion Binding Site Szeltner, Z., Rea, D., Renner, V., Fulop, V., Polgar, L. (2002) J Biol Chem 277: 42613
Substrate-Dependent Competency of the Catalytic Triad of Prolyl Oligopeptidase Szeltner, Z., Rea, D., Juhasz, T., Renner, V., Mucsi, Z., Orosz, G., Fulop, V., Polgar, L. (2002) J Biol Chem 277: 44597
Structures of Prolyl Oligopeptidase Substrate/ Inhibitor Complexes. Use of Inhibitor Binding for Titration of the Catalytic Histidine Residue Fulop, V., Szeltner, Z., Renner, V., Polgar, L. (2001) J Biol Chem 276: 1262
Catalysis of Serine Oligopeptidases is Controlled by a Gating Filter Mechanism Fulop, V., Szeltner, Z., Polgar, L. (2000) EMBO Rep 1: 277
Prolyl Oligopeptidase: An Unusual Beta-Propeller Domain Regulates Proteolysis Fulop, V., Bocskei, Z., Polgar, L. (1998) Cell 94: 161
Organizational Affiliation:
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, PO Box 7, H-1518 Budapest 112, Hungary.
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