The Pectolytic Enzymes and Their Activities in Cultures of Xanthomonas malvacearum (Smith) Dowson

Abstract

Summary The pectolytic enzymes, pectinmethyl galacturonase (PMG), polygalacturonase (PG), polygalacturonate trans-eliminase (PGTE), and pectin methylesterase (PME), were sensitized differentially by varied carbon sources in culture of Xanthomonas malvacearum . PG activities ensured release of mono- and poly-galacturonides from NaPP-substrate. Potato maceration too was effectuated. Enzyme-substrate incubation at 30 °C for 60 min was optimum for PMG and PG elaboration. PME was activated best with 4 h of incubation. PMG and PME were pectin-inducible. PG and PGTE were NaPP-adaptive. However, pectin was equally effective for PG secretion. Addition of glucose to pectin repressed PGTE, PMG, and PG extrusion when added separately to NaPP. Glucose and CMC had retardatory effect on PMG and PGTE excretion. CMC, in combination with pectin, also reduced PME and PG activities. Individually glucose and maltose were poor carbon sources for production of these enzymes by the pathogen. Exo-PG activity, leading to NaPP-substrate break-down and release of galacturonides in varying proportions, was evident in filtrate of 24- and 48-hour-old cultures. Additionally, endo-PG activity picked up well in 72-hour-old culture. Such situations were uniformly true of enzymes obtained from NaPP-, glucose-, maltose-, and pectin-supplied culture filtrates. Separate addition of glucose to NaPP and to pectin, and of CMC to pectin exhibited synergic influence on filtrate which engineered more of galacturonide liberation from the substrate. Individually, maltose was a better source than glucose for inducing exo-PG activity. Potato disc maceration was best effectuated by 48-hour-old culture filtrate. It was optimum for enzyme obtained from NaPP-supplied medium. The next best in this regard was pectin + glucose-supplied culture filtrate enzyme.