Pectic enzymes produced by Pseudomonas fluorescens, an organism associated with “pink eye” disease of potato tubers

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Abstract
No pectin methylesterase (PME) activity was observed in crude or dialyzed extracts from macerated potato tuber tissue inoculated with Pseudomonas fluorescens; however, pectic lyase (syn. polygalacturonic acid transeliminase, PATE) activity was observed. Two PATE enzymes (peaks 1 and 2) were eluted from a pH 9.4 DEAE-cellulose column using a gradient of pH 7.6 Tris-HCl buffer (0.01–0.1 M). Enzyme in peak 1 was about 6 times more active than enzyme in peak 2 based on reducing group assays, and 10 times more active in viscosity reduction of 1% Na-polypectate (NaPP) at pH 8.5. No increase in absorbancy was observed at 515 nm of clarified reaction mixtures, indicating that saturated oligouronides did not accumulate. Other properties of the two peaks: optimum pH range was 8.5–9.5, substrate preference was NaPP vs. pectin, addition of Ca2+ (0.001 M) enhanced activity while EDTA (0.001 M) decreased activity to [Formula: see text], cellulose acetate electrophoresis revealed one band of protein per peak, and heat of inactivation was 51–60C. Thin-layer chromatography of hydrolytic products from NaPP revealed unsaturated uronides and pectic fragments after 2 h hydrolysis; after 96 h hydrolysis only unsaturated uronides were observed. Molecular weight estimations by Sephadex G-200 gel filtration were about 18 000 (peak 1) and 22 500 (peak 2). Enzyme in either peak macerated 400-μ sections of potato tissue.
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