PURIFICATION AND CHARACTERIZATION OF 2 PECTINMETHYLESTERASE FROM PERSIMMON (DIOSPYROS-KAKI)

Two pectinmethylesterase isoforms, PME I and PME II, have been separat ed and purified from persimmon using chromatography techniques. Both i soforms 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 value s (PME I: 54 mu g ml(-1), PME II: 31 mu g ml(-1)). They differed in th eir optimum pH and thermal stability, PME I being the more thermostabl e isoform. Both isoforms exhibited similar behaviour with respect to C a2+ and Na+ concentrations and were strongly inhibited by CaCl2 concen trations of over 80 mM and by NaCl concentrations of over 500 mM. Both isoforms were activated by low concentrations of polygalacturonic aci d and were competitively inhibited by D-galacturonic acid and high con centrations of polygalacturonic acid.