pH-, temperature- and time-dependent activities of endogenous endo-β-D-xylanase, β-D-xylosidase and α-L-arabinofuranosidase in extracts from ungerminated rye (Secale cereale L.) grain

Activities of endogenous beta -D-xylosidase (EC.3.2.1.37). alpha -L-arabinofuranosidase (EC. 3.2.1.55) and endo-beta -D-xylanase (EC.3.2.1.8) were quantified in extracts from ungerminated rye (Secale cereale L., var. Amando) grain. pH- and temperature optimum and stability of the unpurified enzymes were examined. The activity of beta -xylosidase and alpha -arabinofuranosidase against p-nitrophenyl-glycosides was 180 and 346 pkatal/g grain, respectively (pH 4.5: 30 degreesC) and that of the endo-xylanase against RBB-xylan was 11 pkatal/g grain (pH 4.5: 40 degreesC). The pH optimum of each for the enzymes was 4.5, which is similar to the pH of a rye dough. The temperature optima for the enzymes were 40 degreesC (endo-xylanase), 70 degreesC (beta -xylosidase) and 60 degreesC (alpha -arabinofuranosidase), respectively. Sodium chloride (0.5 3.0%, w/v) had no effect on the enzyme activities. The enzymes were relatively stable at pH 4.5 and room temperature for at least 24 h. The enzymes showed no significant decrease in activity when extracts were incubated at pH 4.5 and 30 40 degreesC for 80 120 min. Incubation at temperatures higher that 40 degreesC resulted in a significant decrease in activity. The rate of hydrolysis of the respective p-nitrophenyl glycosides and RBB-xylan was under conditions typical for the rye dough production stages but decreased at temperatures typically encountered in the baking process. (C) 2001 Academic Press.