Characterisation of the first wheat (Triticum aestivum L.) nucleotide pyrophosphatase/phosphodiesterase resembling mammalian counterparts

A formerly unknown nucleotide pyrophosphatase/phosphodiesterase (NPP) of wheat (Triticum aestivumL.) (TaNPP) was recombinantly produced in Pichia pastoris (TaNPPr) following assembly of the sequenceout of wheat ESTs using sequences of known NPPs. Simultaneously, a phosphodiesterase was purified tohomogeneity from wheat germs, characterised and identified as TaNPP. TaNPP contains the highlyconserved catalytic substrate and metal binding residues and displays properties [high pH optimum,glycosylation, high thermostability and inhibition by EDTA and adenosine 50-monophosphate (AMP)]similar to those of mammalian enzymes characterised earlier. The sequence of TaNPP includes that ofa putative transmembrane domain, a characteristic of most NPPs. Both recombinant and native TaNPPpartially occur as oligomeric proteins on SDS PAGE. Upon addition of DTT, both migrate as monomericproteins. Part of the native wheat protein even occurs in its truncated form, thus lacking the transmembraneregion. Out of a range of tested natural substrates, TaNPP had the highest affinity towardsadenine containing nucleotides. While Michaelis-Menten kinetics were valid in the low substrateconcentration range, at higher concentrations, they were no longer applicable. TaNPP shows no similarityto the recently characterised rice and barley enzymes and, is hence, one of the first characterised plantNPPs resembling mammalian NPPs.

Publication year:2010

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BOF-publication weight:2

CSS-citation score:1

Authors from:Higher Education

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