Two isoforms of a nucleotide‐sugar pyrophosphatase/phosphodiesterase from barley leaves (Hordeum vulgare L.) are distinct oligomers of HvGLP1, a germin‐like protein

Two isoforms of ADPglucose pyrophosphatase/phosphodiesterase (AGPPase) have been characterized using barley leaves (Hordeum vulgare L.). Whilst one of the isoforms, designated as soluble AGPPase1 (SAGPPase1), is soluble in low ionic strength buffers, the other, SAGPPase2, is extractable using cell wall hydrolytic enzymes or high salt concentration solutions, thus indicating that it is adventitiously bound to the cell wall. Both AGPPase isoforms are highly resistant to SDS, this characteristic being utilized to purify them to homogeneity after zymographic detection of AGPPase activity in SDS-containing gels. N-terminal and internal amino acid sequencing analyses revealed that both SAGPPase1 and SAGPPase2 are distinct oligomers of the previously designated HvGLP1, which is a member of the ubiquitously distributed group of proteins of unknown function designated as germin-like proteins (GLPs).