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Re: pomegranate seed chitinase III?
joylovepeace Views: 1,480
Published: 7 years ago
This is a reply to # 1,946,717

Re: pomegranate seed chitinase III?

Chitinase III in pomegranate seeds (Punica granatum Linn.) – a high‐capacity calcium‐binding protein in amyloplasts

Chitinase is a class of ubiquitous proteins widely distributed in plants. Defense is the major natural role for chitinase, primarily against fungal pathogens. Little is known of its non‐defensive roles. In this study, a new class III chitinase from pomegranate seeds (PSC) was isolated and purified to homogeneity. The native state of PSC is a monomer with a molecular weight of ∼30 kDa. This chitinase naturally binds calcium ions with high capacity and low affinity, suggesting that PSC is a Ca‐storage protein. Consistent with this idea, its amino acid sequence inferred from cDNA is rich in acidic amino acid residues, especially Asp, similar to reported Ca‐storage proteins. The presence of calcium considerably improves the stability of the protein while having little effect on its enzymatic activity. Transmission electron microscopy (TEM) analyses indicate that, similar to phytoferritin, this enzyme is widely and largely distributed in the stroma of amyloplast of the embryonic cells, suggesting that amyloplast in seeds could serve as an alternative plastid for calcium storage. Indeed, TEM results showed that, within the embryonic cells, calcium ions are mainly distributed in the stroma of the amyloplast, consistent with the role of PSC in calcium storage. Thus, the plant seems to have evolved a new mode for calcium storage in seeds. During seed germination, the content of this enzyme decreases with time, suggesting that this enzyme is involved in this process

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