Resumen
A non-calcium sensitive pectin, with a degree of esterification (DE) of 73%, was demethylated at pH 7.5 with a monocomponent preparation of a thermally tolerant pectin methylesterase (TT-PME, EC 3.1.1.11) isolated from citrus fruit tissue. The DE of the parent pectin (73%) was lowered to 66.5% and 59%. Endo polygalacturonase (EPG) was used to digest the pectin and estimate the maximum length of methyl-protected blocks in the homogalacturonan (HG). Following enzymatic demethylation and EPG digestion, the pectin was exhaustively demethylated with 0.1 M LiOH. Methyl-protected block size was estimated by high performance anion exchange chromatography coupled to an evaporative light scattering detector. The largest EPG protected block for the 66.5% DE pectin was a 19-mer although GA oligomers up to 44 residues were observed for the 59% DE pectin.
