Pectin exopolygalacturonase

Erwinia chrysanthemi synthesizes and secretes a large number of pectinases. The major pectinases include a pectin methylesterase PemA and five isoenzymes of endo-pectate lyases PelA, PelB, PelC, PelD and PelE. In addition, secondary pectinases were identified a pectin methylesterase PemB, two endo-pectate lyases PelL and PelZ, an exo-pectate lyase PelX and an exopolygalacturonase, PehX. The regulation of pectinase synthesis is very complex and dependent on many environmental conditions. It is induced by pectin catabolic products and affected by growth phase, catabolite repression, osmolarity, iron or oxygen starvation... 

The activities of pectic enzymes present in cultivation medium (98 mg of protein extracted from 2.5 1 of pectin medium) were poor, not leading to the clarification of cultivation medium indicating the cleavage of pectate chains, with values 0.024 pmol/min.mg for polygalacturonase, 0.004 pmol/min.mg for exopolygalacturonase, 0.034 pmol/min.mg for pectinesterase and 0.005 pmol/min.mg for pectin lyase. The production of individual pectic enzymes was dependent on the C-source used in the cultivation medium (Tab. 1). 

Pectinesterase activity expressed as a unit corresponding to the microequivalent of ester bonds of pectin molecule, which were hydrolyzed during 1 min. at 45 °C and pH 5.0 under the conditions, which were optimum for these enzymes. Endopolygalacturonase and exopolygalacturonase activities were determined using a technique determined by Ufshitz [8]. Activity of pectintranseliminase was determined by procedure (lOJ. 

Hydrolysis pectate pectin endopolygalacturonase endopolymethylgalacturonase exopolygalacturonase exopolymethylgalacturonase... 

---