CHARACTERIZATION OF GALACTOSE-INDUCED EXTRACELLULAR AND INTRACELLULARPECTOLYTIC ACTIVITIES FROM THE EXO-1 MUTANT STRAIN OF NEUROSPORA-CRASSA

Pectolytic enzymes from the hyperproducer exo-1 mutant of Neurospora c rassa are induced either by pectin or galactose, Galactose-induced pec tinases, in contrast with pectin-induced enzymes, are not affected by glucose repression. Here, the pectolytic enzymes induced by galactose were purified and characterized. Extracellular pectolytic activities w ere separated into two main fractions, Pool I contained lyases, and a polygalacturonase (PG) copurifying as a complex of about 80 kDa (gel f iltration), Pool II contained PG only. Under urea-SDS-PAGE the lyases and polygalacturonase from pool I migrated with an apparent MW of 56.2 kDa, and 34.3 kDa, respectively, PG from pool II exhibited an apparen t MW of 44.7 kDa, Cell extracts contained PG free of lyase activities. Purified intracellular PG migrated (SDS-PAGE) as a single band of app arent MW of 31,5 kDa, All pectinases were glycoproteins (18.5-39% carb ohydrate), with stability and optimum pH at 5-6 and 9-10 for PG and ly ases, respectively. Temperature optima were 40-50 degrees C, respectiv ely. AII enzymes were inactivated at 60 degrees C, with a half-life fr om 1.5 to 5 min, Activation energy (Ea) values for extracellular and i ntracellular PG varied between 0.45 and 2.0 Kcal mol(-1). Pool II and intracellular PG and lyases, exhibited a random mechanism of hydrolysi s. Pool I Pa exhibited an exo character.