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. Author manuscript; available in PMC: 2012 Mar 1.
Published in final edited form as: Mol Microbiol. 2011 Jan 6;79(5):1194–1203. doi: 10.1111/j.1365-2958.2010.07500.x

Table 1.

Kinetic parameters of Clostridium Grx forms

Protein kcat (min−1) Km (HED) (mM) kcat/Km (mM−1 min−1)
cGrx1 87 ± 15 1.5 ± 0.4 58
cGrx1/U13C 0.5 ± 0.1 1.5 ± 0.8 0.3
cGrx1/U13W ND - -
cGrx1/C16S 83 ± 8 0.9 ± 0.2 92
cGrx2 186 ± 28 17.6 ± 5.6 11
cGrx2/C15S 396 ± 67 18.1 ± 4.5 22
eGrx1 126 ± 8 11.2 ± 2.2 11

Purified proteins were assayed in the standard Grx reaction using HED as a substrate. Km and kcat values were determined by fitting the experimental data to the Michaelis-Menten equation. The protein concentrations of selenoprotein Grxs (cGrx1 and cGrx1/C16S) were normalized by subtracting the concentrations of Trp-inserted forms and subjected to calculating kcat values. cGrx1, wild-type selenoprotein Clostridium Grx1; cGrx1/U13C, Sec-to-Cys mutant of cGrx1; cGrx1/U13W, Sec-to-Trp mutant of cGrx1; cGrx1/C16S, monoselenol mutant of cGrx1; cGrx2, wild-type Cys-containing Clostridium Grx2; cGrx2/C15S, monothiol mutant of cGrx2; eGrx1, E. coli Grx1. ND, activity not detectable.