Purification and characterization of a polygalacturonase from Rhizoctonia solani AG-3

MACHINANDIARENA, M.; PATIÑO, B.; DALEO, G.; VAZQUEZ, C.; GONZALEZ-JAÉN, M.T.

Anaheim, California, EE UU

Congreso; Annual Meeting of The American Phytopathological Society.; 2004

Rhizoctonia canker is considered a major important disease of potato. The disease is caused by Rhizoctonia solani. Most isolates of R. solani pathogenic to potato belong to anastomosis group 3 (AG-3). The mechanisms of pathogenicity and symptom induction by this fungus are poorly understood despite many ultrastructural, biochemical and genetics studies. We have studied the production of pectinolytic enzymes by this fungus during growth in vitro on pectin as carbon source, for the analysis of the role in pathogenicity of the major extracellular pectinolytic enzymes produced by R. solani AG-3. In the present work we report, for the first time, the purification of an extracellular endo-poligalacturonase (endoPG) from Rhizoctonia solani AG3. This enzime was purified by two anion-exchange chromatography steps. The molecular mass was estimated to be 40 kDa after SDS-PAGE and HPLC gel filtration and has an pI of 4.25. The optimum temperature for this enzyme was at 45°C. The activity remained stable up to 40°C and was rapidly inactivated after incubation at temperatures above 50°C. The optimum pH was 5.5. The endo PG was active on polygalacturonic acid and esterified pectin, but the activity on pectin decrease with an increase in esterification. The enzyme released a series of oligo-galacturonates from poligalacturonic acid with a degree of polymerization above trimer. The enzyme did not present activity on digalacturonic and trigalacturonic acid.