Abstract

An enzyme with apparent dual functions as a xylanase and carboxymethylcellulase was purified from the major soldier salivary glands of the termite Macrotermes subhyalinus. The preparation was found homogeneous by gel electrophoresis after successive chromatography on anion-exchange, cation-exchange and hydro- phobic interaction columns. The specific activities towards carboxymethylcellulose and xylan were respectively 3.59 and 5.68 U/mg of protein. The molecular weight was measured to be 57.12 kDa by gel filtration and 14.47 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme showed a pH optimum of 5.6 for carboxymethylcellulase activity and 5.0 for xylanase activity. The optimum temperature for carboxymethylcellulase and xylanase activities was respectively 60 and 65°C. The enzyme was capable of hydrolyzing both beta-1,4-glycosidic and beta-1,4-xylosidic bonds in carboxymethylcellulose and xylans, respectively. Based on thin-layer chromatographic analysis of the degradation products, the carboxymethylcellulase activity produced glucose, cellobiose and cellodextrins from carboxymethylcellulose as the substrate. When xylan from Birchwood was used, end products were xylobiose and xylodextrins. The salivary glands of M. subhyalinus soldier apparently produce an endo-beta-xylanase with dual activity against carboxymethylcellulose. The apparent role of this enzyme in the digestive tract is the hydrolysis of xylan and potentially cellulose.

Key words: Endo-beta-D-glucanase, endo-beta-D-xylanase, major soldier, physiological role, salivary glands, termite Macrotermes subhyalinus.