Synthesis and excretion of polygalacturonic acid trans-eliminase in Erwinia, Yersinia, and Klebsiella species

Abstract

Various enterobacteria exhibit several patterns of synthesis and excretion of polygalacturonic acid trans-eliminase (PATE), one of the enzymes involved in degradation of pectic substances. In a strain of Erwinia chrysanthemi, PATE is an extracellular enzyme and is almost totally excreted. In strains of Yersinia enterocolitica and Yersinia pseudotuberculosis, PATE is a periplasmic and cytoplasmic enzyme. In a strain of Erwinia carotovora, PATE activity is extracellular, periplasmic, and cytoplasmic. In an "oxytocum" strain of Klebsiella pneumoniae, PATE is entirely cytoplasmic; none is found in the periplasm and almost none in culture supernatants. Cells (but not supernatants, because PATE is not excreted) of K. pneumoniae show much higher levels of PATE activity when grown on polygalacturonate than when grown on other carbon sources. A clinical strain of Y. enterocolitica synthesizes high levels of PATE activity (almost all cell-bound) when grown in the presence of gluconate, glycerol, or polygalacturonate, and considerably less activity when grown on glucose. A clinical strain of Y. pseudotuberculosis synthesizes barely detectable quantities of cell-bound PATE regardless of the carbon source. The phytopathogenic Erwinia strains synthesize and excrete high levels of PATE activity when grown on polygalacturonate, galacturonate, gluconate, or glycerol. Growth on glucose represses PATE activity in the Erwinia strains; the extent of repression differs between the two strains. The different patterns of synthesis and excretion are discussed in the light of the possible catabolic and (or) cytolytic (plant tissue-macerating) functions and the related ecological significance of PATE in these enterobacteria.