Pectate, Pectin, and Poly-D-Galacturonate Lyases

The stability of pectate and pectin depolymerizing enzymes produced by Mucor puriformis, Rhizopus sexualis, R. stolonifer, Botrytis cinerea, Aureobasidium pullulans, Trichosporon pullulans, and Cryptococcus albidus var. albidus in sulphite liquor has been studied in relation to the breakdown of sulphited strawberries. Marked breakdown of fruit occurred only when pectolytic activity could be detected in the liquor for more than two weeks using a viscometric assay. Of the fungi tested, Rhizopus species produced enzymes that were the most stable in sulphite liquor. For each of the Mucor and Rhizopus species tested, the stability of poly-D-galacturonases in sulphite liquor was very similar for extracts of infected fruit and culture filtrates. It was suggested that sulphite labile (=acid labile) and sulphite stable (=acid stable) forms of the poly-D-galacturonases are present. 

A pectinolytic bacterium isolated from a mixed microbial population by means of a chemostat enrichment procedure was identified as Erwinia carotoyora, It grew only on highly methylated pectin and produced a pectin lysase which released unsaturated monomer and dimer from 71% esterified citrus pectin. The pectin lyase was inducible only by pectins having a high methyl ester content. 

Various enterobacteria have been shown to exhibit several patterns of biosynthesis and excretion of poly-D-galacturonate lyase.In a strain of Erwinia chrysanthemi, poly-D-galacturonate lyase is an extracellular enzyme and is almost totally excreted. In strains of Yersinia enterocolitica and Yersinia pseudotuberculosis poly-D-galacturonate lyase is a periplasmic and cytoplasmic enzyme. 

The poly-D-galacturonate lyase associated with healthy and Gloeosporium papayae rot infected papaya Carieca papaya) fruit, and secreted in papaya pulp medium by the pathogen has been investigated.  

Production of enzymes degrading plant cell walls has been studied using media containing cellobiose or ammonium ions as limiting nutrients. Pectin lyase was primarily cell-associated during exponential growth in batch culture but accumulated in the supernatant during the stationary phase. 

The pectic enzymes of six strains of pigmented, pectolytic Clostridia isolated from potatoes have been examined and compared with those of strains of Clostridium felsineum and C. aurantibutyricum using cup-plate assays. All the organisms were found to produce pectate lyase activity. 

4-0-(4-Deoxy- -L-//rreo-hex-4-enepyranosyluronic acid)-D-galacturonic acid has been proposed as the inducer of pectic acid (poly-D-galacturonate) lyase in Erwinia carotovora. No induction was observed for D-galacturonic acid. 

The taxonomy of the brown rot fungi (Monilinia species) has been related to their extracellular cell wall-degrading enzyme. Patterns of pectin lyase secreted by M. fructigena, M. fructicola, and M. laxa were studied by isoelectric focusing.  

A pectate lyase has been purified from the culture filtrate of Streptomyces fradiae by precipitation with ammonium sulphate, followed by ion-exchange 

The role of the secondary alcoholic groups of D-galacturonan in its degradation by enrfo-D-galacturonanase has been investigated.  

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