An Avicel-affinity Site in an Avicel-digesting Exocellulase from a Trichoderma viride Mutant

概要

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A single form of exo-type cellulase (Exo I ; M_W, 65,000), purified from a Trichoderma viride proteasedepressed mutant, HK-75,digested Avicel to cellobiose exowise, and hydrolyzed cellotriose, cellotetraose, and cellopentaose in the strict manner of splitting off by cellobiose units. Exo I, however, hydrolyzed cellohexaose by both cellobiose and cellotriose units. Exo I was proteolyzed by papain into two fragments ; GPExo (M_W, 9,000) and Exo I' (M_W, 56,000). The GPExo intensively adsorbed onto Avicel but did not hydrolyzed it. Exo I' had nearly identical activity to that of intact Exo I toward cellooligosaccharides but was almost inert to Avicel in digestion and adsorption. Sequence analysis of N-terminal and C-terminal amino acids showed that GPExo was between Gly^<435> and Leu^<496> and Exo I' between Glu^1 and Gly^<434> in Exo I. Exo I therefore consists of two domains, one for adsorption to Avicel, as demonstrated by the Avicel-affinity site, GPExo and the other for the cleavage of glycosidic linkages as demonstrated in Exo I'.
社団法人日本農芸化学会の論文
1992-10-23