Purification and characterization of a pectin-releasing enzyme produced by Kluyveromyces wickerhamii

A pectin-releasing enzyme produced by Kluyveromyces wickerhamii IFO 1675 (PPase-W) was purified to homogeneity from a culture filtrate by cation-exchange and size-exclusion chromatographies. This enzyme had a molecular weight of 35,000 determined by both size exclusion chromatography and ultracentrifugal analysis, and of 40,000 by SDS-PAGE. It contained 2.4% sugar, and its isoelectric point was at pH 5.2. PPase-W catalyzed the release of highly polymerized pectin from various protopectins, and also showed endopolygalacturonase (endo-PGase) activity. The purified enzyme had optimum PGase activity at about pH 5.2 and 50°C and was stable in the range of pH from 4.0 to 7.0 and up to 50°C. The properties of PPase-W were compared with those of PPase-F from Kluyveromyces fragilis IFO 0288, and some differences were found. Also, some preliminary data dealing with the relationship between enzyme activities (PPase and endo-PGase) and protein structure are discussed.