Degradation of pectic polysaccharides extracted from suspension cultures of carrot by purified exo‐polygalacturonase

Highly purified exo‐polygalacturonase was obtained from suspension cultures of carrot ( Daucus carota L. cv. Kintoki) by dialysis at pH 5.2, chromatography on DEAE‐Sephadex A‐50 and on Sephadex G‐150, and preparative polyacrylamide disc gel electrophoresis. The enzyme did not attack the isolated carrot cell walls directly, but it had some effect on pectic polysaccharides extracted from the walls. The extracted polysaccharides were fractionated by DEAE‐Sephadex A‐50 column chromatography yielding four carbohydrate fractions. The major fraction (P‐3) was then reacted with the exo‐polygalacturonase. The enzyme treatment resulted in hydrolysis of approximately 18% of the glycosyl linkages of fraction P‐3 with the release of galacturonic acids. The molecular size estimated by Bio‐Gel A‐5m gel filtration was not markedly affected by the enzyme action, but the percentage of galacturonosyl residues was clearly reduced. The specific activity of exo‐polygalacturonase changed during the growth cycle, in relation to the cell growth.