scholarly journals pH Dependence of Catalysis byPseudomonas aeruginosaIsochorismate–Pyruvate Lyase: Implications for Transition State Stabilization and the Role of Lysine 42

Biochemistry ◽  
2011 ◽  
Vol 50 (33) ◽  
pp. 7198-7207 ◽  
Author(s):  
Jose Olucha ◽  
Andrew N. Ouellette ◽  
Qianyi Luo ◽  
Audrey L. Lamb
Keyword(s):  
Transition State ◽  
Ph Dependence ◽  
Transition State Stabilization

Functional role of a mobile loop of Escherichia coli dihydrofolate reductase in transition-state stabilization

Biochemistry ◽  
1992 ◽  
Vol 31 (34) ◽  
pp. 7826-7833 ◽  
Author(s):  
Luyuan Li ◽  
Peter E. Wright ◽  
Stephen J. Benkovic ◽  
Christopher J. Falzone
Keyword(s):  
Escherichia Coli ◽  
Transition State ◽  
Dihydrofolate Reductase ◽  
Functional Role ◽  
Transition State Stabilization

scholarly journals Study of the role of the highly conserved residues Arg9 and Arg64 in the catalytic function of human N-acetyltransferases NAT1 and NAT2 by site-directed mutagenesis

1997 ◽  
Vol 323 (1) ◽  
pp. 207-215 ◽  
Author(s):  
Claudine DELOMÉNIE ◽  
Geoffrey H. GOODFELLOW ◽  
Rajagopal KRISHNAMOORTHY ◽  
Denis M. GRANT ◽  
Jean-Marie DUPRET
Keyword(s):  
Ph Dependence ◽  
Conformational Stability ◽  
Base Catalysis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Base Catalysts ◽  
General Base ◽  
Catalytic Function ◽  
Transition State Stabilization

The arylamine N-acetyltransferases (NATs) NAT1 and NAT2 are responsible for the biotransformation of many arylamine and hydroxylamine xenobiotics. It has been proposed that NATs may act through a cysteine-linked acetyl-enzyme intermediate in a general base catalysis involving a highly conserved arginine residue such as Arg64. To investigate this possibility, we used site-directed mutagenesis and expression of recombinant human NAT1 and NAT2 in Escherichia coli. Sequence comparison with NATs from other species indicated that Arg9 and Arg64 are the only invariant basic residues. Either mutation of the presumed catalytic Cys68 residue or the simultaneous mutation of Arg9 and Arg64 to Ala produced proteins with undetectable enzyme activity. NAT1 or NAT2 singly substituted at Arg9 or Arg64 with Ala, Met, Gln or Lys exhibited unaltered Km values for arylamine acceptor substrates, but a marked loss of activity and stability. Finally, double replacement of Arg9/Arg64 with lysine in NAT1 altered the Km for arylamine substrates (decreased by 8-14-fold) and for acetyl-CoA (elevated 5-fold), and modified the pH-dependence of activity. Thus, through their positively charged side chains, Arg9 and Arg64 seem to contribute to the conformational stability of NAT1 and NAT2 rather than acting as general base catalysts. Our results also support a mechanism in which Arg9 and Arg64 are involved in substrate binding and transition-state stabilization of NAT1.

Role of Charged Residues in the Catalytic Mechanism of Hepatitis C Virus NS3 Protease:  Electrostatic Precollision Guidance and Transition-State Stabilization

Biochemistry ◽  
2001 ◽  
Vol 40 (3) ◽  
pp. 631-640 ◽  
Author(s):  
Uwe Koch ◽  
Gabriella Biasiol ◽  
Mirko Brunetti ◽  
Daniela Fattori ◽  
Michele Pallaoro ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Transition State ◽  
Catalytic Mechanism ◽  
Transition State Stabilization ◽  
Charged Residues ◽  
Ns3 Protease
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