Hydrolyzes chitin. Probable calcium storage protein of the seeds. Binds calcium ions with high capacity and low affinity. Involved in seed germination. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Activity is not affected by addition of 10 mM Ca(2+) or removal of Ca(2+). kcat/KM is 0.119 M(-1)sec(-1) for native protein, 0.130 M(-1)sec(-1) for native protein with 10 mM Ca(2+) and 0.116 M(-1)sec(-1) for EDTA-treated protein, using 4-methylumbelliferyl-beta-D-N,N',N''-triacetylchitotrioside (4-MU(GlcNAc)(3)) as substrate at pH 4.5 and 37 degrees Celsius. Optimum pH is between 2.5 and 5.0. Removal of Ca(2+) from the protein by EDTA treatment narrows the pH range to 2.5-3.5. Optimum temperature is approximately 45 degrees Celsius. Removal of Ca(2+) from the protein by EDTA treatment decreases the optimum temperature to 35 degrees Celsius. Monomer. Localizes to stroma in amyloplasts of the embryonic cells of the seed. Highly expressed in seeds and to a lesser extent in the skin of the pomegranate fruit (at protein level). Not expressed in leaves or flesh of the fruit (at protein level). Expressed at all stages of seed germination. Expression decreases markedly from day 1 to day 15 after imbibition. The measured mass is that of EDTA-treated protein to remove Ca(2+). The measured mass is that of protein without EDTA-treatment to retain Ca(2+). The measured mass is that of protein with three disulfide bridges. Causes an allergic reaction in human. Binds to IgE in 19% of 357 patients allergic to pomegranate. Belongs to the glycosyl hydrolase 18 family. Chitinase class III subfamily.