Partial Characterization of C(x) Cellulase and Cellobiase from Ripening Tomato Fruits

Cellulolytic enzymes were studied in extracts from the locular contents of ripening fruits of Lycopersicon esculentum var. KC-146. When acting on carboxymethyl cellulose, the enzyme preparations were capable of decreasing the viscosity of the reaction mixture and generating reducing groups, oligosaccharides, and glucose. Cellobiose cellotriose, cellotetrose, and cellopentose also served as substrates for glucose production.These properties were due to the presence in the extracts of two cellulolytic enzymes-C(x) cellulase (E.C. 3.2.1.4) and cellobiase- (E.C. 3.2.1.21). No evidence was found for the presence of exocellulase or C(1), an enzyme which initiates enzymatic attack on insoluble cellulose.Cellobiose was found to be weakly inhibitory to C(x) cellulase. d-Glucono-1,5-lactone competitively inhibited cellobiase. The K(m) for cellobiose was 0.34 mm, and the K(i) for gluconolactone was 23 muM.