REGULATION OF PECTIC ENZYMES FROM THE EXO-1 MUTANT STRAIN OF NEUROSPORA-CRASSA - EFFECTS OF GLUCOSE, GALACTOSE, AND GALACTURONIC ACID

The exo-1 mutant of Neurospora crassa produced and secreted pectolytic activities when incubated in the presence of pectin-containing biolog ical materials. This study shows that polygalacturonase, pectate lyase and pectin lyase activities were induced in media supplemented with g alactose or galacturonic acid, indicating that these sugars induced th e synthesis of pectinases. Pectinesterase activity was undetectable. P olygalacturonase activity was better induced by galactose than by gala cturonic acid. The reverse was true for lyase activities. The inducing effect of galactose and galacturonic acid seemed to be different: (i) a mixture of galactose and galacturonic acid synergistically increase d the production of pectic enzymes, as compared to that in the presenc e of one of these sugars; (ii) the inducing effect of galacturonic aci d was partially repressed by glucose; (iii) in contrast, the inducing effect of galactose, rather than repressed, was enhanced by the presen ce of glucose. Altogether, these data point out to a complex mechanism of regulation of pectolytic enzymes by organic substances.