Cellobiase activity in three species of Australian termites

Abstract

The cellobiase of the higher termite Nasutitermes exitiosus was located in the foregut (8%) and the midgut (92%). In N. walkeri 97% of the activity was in the midgut, 2% in the foregut and 1% in the mixed segment. Most of the cellobiase activity in the lower termite Coptotermes lacteus was in the hindgut (78%) and the midgut (21%) with traces (1%) in the foregut. Removal of the protozoa and spirochaetes by oxygen treatment resulted in loss of most of the cellulase and cellobiase from the hindgut within 28 hr of treatment; the midgut enzymes were unaffected. Isolated protozoa had cellulase and cellobiase of high specific activity and accounted for most of the total cellulolytic activity in the hindgut. These results indicate that the enzymes in the midgut are secreted by all three termites, whereas the enzymes in the hindgut ( C. lacteus only) are of protozoal origin. The optimum pH for cellobiase from N. exitiosus (foregut and midgut) ranged from 4.5 to 7.0; the C. lacteus enzymes had an optimum activity at pH 5.0–6.0. The pH of N. exitiosus gut ranged from 2.0 to 2.8 (foregut), 2.8 to 3.8 (rectum), and from 6.8 to 7.5 (midgut and mixed segment). The pH of the midgut and hindgut of C. lacteus was 6.8–7.4 and foregut was 3.8–4.4. The significance of the gut pH on cellobiase activity is discussed. Crude preparations of C. lacteus cellobiase (both midgut and hindgut) were inactivated at 62°C and were competitively inhibited by 1,5-gluconolactone.