Studies on the Pectic Depolymerases I. : Exopolygalacturonase from Root Tissues and Cell Suspension Cultures of Carrots

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Three polygalacturonases (PG) have been isolated from carrots (Daucus carota L. cv. Kintoki). Two were isolated from root tissues (PG-I and PG-II) and one from cell suspension cultures (PG-III). PG-I and PG-III were readily solubilized in a low ionic strength buffer, whereas PG-II required additional NaCl to be solubilized. These seems to be a change in the properties of PG between the original tissue and carrot cell cultures. The three PGs were partially purified by chromatography on Sephadex G-150, and characterized. Elution from a Sephadex G-150 column indicated a molecular weight of about 48,000 for all three PGs. PG-III, studied in detail, hydrolyzed the galacturonan chain in an exo-fashion, and was not activated by a variety of cations at concentrations of 0.5 or 1.0 mM. The pH optimum, and pH and heat stability of PG-I and PG-III were slightly different from those of PG-II. PG-I was also different from PG-II and PG-III in its pectin hydrolyzing activity. These results indicate that the enzymatic properties of PG-III from cell cultllres are very similar to those of PG.-I or PG-II from root tissues; the only significant difference seems to be the binding properties of the PGs to the cell wall materials.
日本植物生理学会の論文