Modulation of the Activities of Catalase−Peroxidase HPI ofEscherichia coliby Site-Directed Mutagenesis†

Biochemistry ◽  
2000 ◽  
Vol 39 (19) ◽  
pp. 5868-5875 ◽  
Author(s):  
Alex Hillar ◽  
Brian Peters ◽  
Ryan Pauls ◽  
Alexander Loboda ◽  
Haoming Zhang ◽  
...  
2005 ◽  
pp. 3495 ◽  
Author(s):  
Nigel A. J. Eady ◽  
Jesmin ◽  
Spiros Servos ◽  
Anthony E. G. Cass ◽  
Judit M. Nagy ◽  
...  

1999 ◽  
Vol 338 (3) ◽  
pp. 753 ◽  
Author(s):  
Brigitte SAINT-JOANIS ◽  
Hélène SOUCHON ◽  
Martin WILMING ◽  
Kai JOHNSSON ◽  
Pedro M. ALZARI ◽  
...  

1999 ◽  
Vol 338 (3) ◽  
pp. 753-760 ◽  
Author(s):  
Brigitte SAINT-JOANIS ◽  
Hélène SOUCHON ◽  
Martin WILMING ◽  
Kai JOHNSSON ◽  
Pedro M. ALZARI ◽  
...  

A series of mutants bearing single amino acid substitutions often encountered in the catalase/peroxidase, KatG, from isoniazid-resistant isolates of Mycobacterium tuberculosis has been produced by site-directed mutagenesis. The resultant enzymes were overexpressed, purified and characterized. Replacing Cys-20 by Ser abolished disulphide-bridge formation, but did not affect either dimerization of the enzyme or catalysis. The substitution of Thr-275, which is probably involved in electron transfer from the haem, by proline resulted in a highly unstable enzyme with insignificant enzyme activities. The most commonly occurring substitution in drug-resistant clinical isolates is the replacement of Ser-315 by Thr; this lowered catalase and peroxidase activities by 50% and caused a significant decrease in the KatG-mediated inhibition of the activity of the NADH-dependent enoyl-[acyl-carrier protein] reductase, InhA, in vitro. The ability of this enzyme to produce free radicals from isoniazid was severely impaired, as judged by its loss of NitroBlue Tetrazolium reduction activity. Replacement of Leu-587 by Pro resulted in marked instability of KatG, indicating that the C-terminal domain is also important for structural and functional integrity.


2013 ◽  
Vol 37 (3) ◽  
pp. 330
Author(s):  
Yanan WANG ◽  
Xudong LIU ◽  
Linlin MU ◽  
Zhipeng LIU ◽  
Chunmei LI ◽  
...  

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