Enzymatic Studies on a Cellulase System of Trichoderma viride. IV. Purification and Properties of a Less-Random Type Cellulase

Abstract

A cellulase [EC 3. 2. 1. 4] component was purified from a crude cellulase preparation of Trichoderma viride (Meicelase) by consecutive column chromatography procedures, and was designated as cellulase III. The enzyme was homogeneous on polyacrylamide gel disc electrophoresis. The molecular weight of the enzyme was estimated to be about 45,000 by gel filtration. The optimum pH and temperature of the enzyme were pH 4.5–5.0 and 50°, respectively. The enzyme was stable over the range of pH 4.5–7.5 at 4° for 24 hr, and retained 40% of the original carboxymethylcellulose-saccharifying activity after heating at 100° for 10 min. The enzyme was completely inactivated by 1 mM Hg²⁺, and partially by 1 mM Ag⁺ and Cu²⁺. The enzyme was characterized as a less-random type cellulase on the basis of its action on carboxymethylcellulose. The enzyme split cellohexaose, retaining the β-configuration of the anomeric carbon atoms in the hydrolysis products. The K_m values of cellulase III for cellooligosaccharides decreased in parallel with increase of the chain length of the substrates, while V_max values showed a tendency to increase. The enzyme produced predominantly cellobiose and glucose from various cellulosic substrates as well as from higher cellooligosaccharides. Cellulase III preferentially attacked the aglycone linkage of p-nintrophenyl β-D-cellobioside. The enzyme was found to catalyze the rapid synthesis of cellotetraose from cellobiose (condensation action).