Characterization of glycerol dehydratase expressed by fusing its alpha- and beta-subunits.

ABSTRACT

The gdh and gdhr genes, encoding B(12)-dependent glycerol dehydratase (GDH) and glycerol dehydratase reactivase (GDHR), respectively, in Klebsiella pneumoniae, were cloned and expressed in E. coli. Part of the beta-subunit was lost during GDH purification when co-expressing alpha, beta and gamma subunit. This was overcome by fusing the beta-subunit to alpha- or gamma-subunit with/without the insertion of a linker peptide between the fusion moieties. The kinetic properties of the fusion enzymes were characterized and compared with wild type enzyme. The results demonstrated that the fusion protein GDHALB/C, constructed by linking the N-terminal of beta-subunit to the C-terminal of alpha subunit through a (Gly(4)Ser)(4) linker peptide, had the greatest catalytic activity. Similar to the wild-type enzyme, GDHALB/C underwent mechanism-based inactivation by glycerol during catalysis and could be reactivated by GDHR.