In Vitro Secretion of Pectolytic Enzymes by Xanthomonas campestris

Abstract

Summary Xanthomonas campestris (Pammel) Dowson produces pectic enzymes under the influence of different carbon sources. Polymethyl galacturonase (PMG) was a pectin-inducible enzyme in X. campestris , being best extruded with pectin as carbon source. Addition of glucose to pectin had practically no effect, to a smaller extent NaPP (sodium polypectate) effectuated PMG secretion. Addition of CMC to NaPP lowered the PMG secretion, glucose and maltose were found to be poor carbon sources for PMG induction. Polygalacturonase (PG), too, was adaptively produced in the culture filtrate of the pathogen, grown with NaPP as the carbon source. Addition of glucose to NaPP enhanced PG secretion and that of CMC retarded it. Glucose, pectin, and maltose individually caused PG liberation, but in a very minor way. 30 °C and 60 min of enzyme-substrate incubation were found to be optimum physical conditions for the secretion of PMG and PG. Polygalacturonase trans-eliminase (PGTE) was an exo-cellular enzyme, produced by X. campestris under adapted condition with NaPP as the best inducible carbon source. Separate addition of glucose and CMC to NaPP reduced PGTE extrusion. Pectin, glucose, and maltose separately effected PGTE liberation, but to a very limited extent, being much less than with NaPP. Addition of glucose to pectin suppressed whatever PGTE the pectin was alone able to produce.