Partial Purification and Characterization of Pectin Methyl Esterase in Southern Peas (Vigna sinesis)

The purposes of this study were to partially purify pectin methyl esterase (PME) of Southern peas (Vigna sinensis), to determine optimum pH and NaC1 concentration for maximum enzyme activity, to measure the energy of activation and kinetic reactions, and to ascertain the presence of multiple molecular forms of the enzyme and their isoelectric points.

PME was extracted from an acetone powder preparation and purified by a two-step ammonium sulfate fractionation and dialysis. The activity of the partially purified enzyme was significantly (p < 0.05) influenced by pH, NaC1 concentration, and the interaction between pH and NaC1 concentration. The optimum pH and NaC1 concentration were 7.9 and 0.25 M, respectively. The energies of activation were calculated to be 4,900, 5,950, and 6,900 calories/mole at pH 6.0, 7.0, and 7.0, respectively. PME had a K_m of 0.781% pectin N.F. and a V_max of 24.34 PME units.

Additional purification was achieved by means of column chromatography on DEAE-cellulose and Spehadex G-100. The PME preparation thus obtained was subjected to gel electrofocusing. One PME component and two protein components were detected. The isoelectric point of the PME was 4.5 at 20° C.