Decrease in Kcat of fdh protein when cysteine replaces selenocysteine

Value ~300 Fold
Organism Bacteria Escherichia coli
Reference Axley MJ, Böck A, Stadtman TC. Catalytic properties of an Escherichia coli formate dehydrogenase mutant in which sulfur replaces selenium. Proc Natl Acad Sci U S A. 1991 Oct 188(19):pp. 8452PubMed ID1924303
Method Enzyme activity was determined as a function of formate and BV (benzyl viologen) concentrations.
Comments Kcat of original fdh with selenocysteine is 2800 1/sec. In mutant (s)fdh with cysteine replacing selenocysteine kcat=9 1/sec. The diminished catalytic activity is due to a rate of formate oxidation (k2) that is three orders of magnitude lower for [S]FDHH.
Entered by Uri M
ID 102621