Open AccessStabilization of NAD‐dependent formate dehydrogenase from Candida boidinii by site‐directed mutagenesis of cysteine residues
Author(s) -
Slusarczyk Heike,
Felber Stephan,
Kula MariaRegina,
Pohl Martina
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.01123.x
Subject(s) - formate dehydrogenase , biochemistry , site directed mutagenesis , nad+ kinase , enzyme , cysteine , mutant , mutagenesis , dehydrogenase , escherichia coli , chemistry , biology , formate , cofactor , gene , catalysis
The gene of the NAD‐dependent formate dehydrogenase (FDH) from the yeast Candida boidinii was cloned by PCR using genomic DNA as a template. Expression of the gene in Escherichia coli yielded functional FDH with about 20% of the soluble cell protein . To confirm the hypothesis of a thiol‐coupled inactivation process, both cysteine residues in the primary structure of the enzyme have been exchanged by site‐directed mutagenesis using a homology model based on the 3D structure of FDH from Pseudomonas sp. 101 and from related dehydrogenases. Compared to the wt enzyme, most of the mutants were significantly more stable towards oxidative stress in the presence of Cu(II) ions, whereas the temperature optima and kinetic constants of the enzymatic reaction are not significantly altered by the mutations. Determination of the T m values revealed that the stability at temperatures above 50 °C is optimal for the native and the recombinant wt enzyme ( T m 57 °C), whereas the T m values of the mutant enzymes vary in the range 44–52 °C. Best results in initial tests concerning the application of the enzyme for regeneration of NADH in biotransformation of trimethyl pyruvate to l tert leucine were obtained with two mutants, FDHC23S and FDHC23S/C262A, which are significantly more stable than the wt enzyme.