Kinetic and thermodynamic properties of two barley thioredoxin h isozymes, HvTrxh1 and HvTrxh2
Research output: Contribution to journal › Journal article › Research › peer-review
Barley thioredoxin h isozymes 1 (HvTrxh1) and barley thioredoxin h isozymes 2 (HvTrxh2) show distinct spatiotemporal distribution in germinating seeds. Using a novel approach involving measurement of bidirectional electron transfer rates between Escherichia coli thioredoxin, which exhibits redox-dependent fluorescence, and the barley isozymes, reaction kinetics and thermodynamic properties were readily determined. The reaction constants were approximately 60% higher for HvTrxh1 than HvTrxh2, while their redox potentials were very similar. The primary nucleophile, Cys(N), of the active site Trp-Cys(N)-Gly-Pro-Cys(C) motif has an apparent pK(a) of 7.6 in both isozymes, as found by iodoacetamide titration, but showed approximately 70% higher reactivity in HvTrxh1, suggesting significant functional difference between the isozymes.
|Number of pages||4|
|Publication status||Published - 2010|
Keywords: Thioredoxin; Dithiol/disulfide exchange; Tryptophan fluorescence; Redox potential; Thiol pKa