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Purification and characterisation of two pectinmethylesterase from persimmon (Diospyros kaki)

Alonso, J., Howell, N., Canet, W.
Journal of the science of food and agriculture 1997 v.75 no.3 pp. 352-358
Diospyros kaki, pectinesterase, purification, molecular weight, isozymes, enzyme activity, pH, heat stability, sodium, calcium chloride, sodium chloride, polyuronides, galacturonic acid, inorganic ions, calcium
Two pectinmethylesterase isoforms, PME I and PME II, have been separated and purified from persimmon using chromatography techniques. Both isoforms presented differences in molecular weight (PME I: 51 kDa, PME II: 30 kDa), isoelectric point (PME I: 8.4, PME II: 6.9) and K(m) values (PME I: 54 micrograms ml-1, PME II: 31 micrograms ml-1). They differed in their optimum pH and thermal stability, PME I being the more thermostable isoform. Both isoforms exhibited similar behaviour with respect to Ca2+ and Na+ concentrations and were strongly inhibited by CaCl2 concentrations of over 80 mM and by NaCl concentrations of over 500 mM. Both isoforms were activated by low concentrations of polygalacturonic acid and were competitively inhibited by D-galacturonic acid and high concentrations of polygalacturonic acid.