Journal of Cereal Science vol:51 issue:3 pages:319-325
We cloned the first nudix hydrolase of wheat (Triticum aestivum L.) (TaNUDT1) and expressed it using
Escherichia coli as expression host. Properties of the purified His6-tagged protein were studied. The
sequence codes for a nudix hydrolase with a molecular mass of around 43x103 and a predicted pI of 5.68.
The characteristic residues of the nudix box were highly conserved in the wheat enzyme sequence, and
TaNUDT1 is most probably targeted to the peroxisomes. In the presence of dithiothreitol and MnCl2, the
enzyme hydrolyses the nicotinamide coenzymes NAD(P)(H) as could be predicted by the presence of
a conserved amino acid array C-terminal to the nudix box, and the enzyme has higher affinity towards
the reduced forms of the coenzymes. In light of previous reports of nudix enzymes and the physiological
concentration of their substrates, we found its Km values towards some of the coenzymes to be relatively
high. As NAD(P)(H) and FAD play crucial roles in cell metabolism, extensive hydrolysis could be detrimental
to cell functioning. We speculate that a decreased enzyme affinity may point to a built-in
restriction on coenzyme hydrolysis in vivo. Furthermore, by hydrolysing the cofactors of several redox
enzymes, this enzyme may well affect several wheat based processes.