The 1,4-beta-D-glucan glucanohydrolases from Phanerochaete chrysosporium. Re-assessment of their significance in cellulose degradation mechanisms.
A physico-chemical, functional and structural characterization, including partial sequence data, of three major 1,4-beta-D-glucan glucanohydrolases (EC. 3.2.1.4) isolated from the culture filtrate of the white-rot fungus Phanerochaete chrysosporium, shows that all three enzymes belong to a single family of cellulases. EG44, pI 4.3, (named after its apparent molecular mass in kDa), shows a clear homology with Schizopyllum commune Endoglucanase I (EGI); whereas EG38, pI 4.9, (named in the same manner) is related more closely to Trichoderma reesei (Trichoderma longibrachiatum) Endoglucanase III (EGIII). EG36, pI 5.6-5.7, is probably an EG38 protein lacking its cellulose binding domain. Strong synergistic action is induced by the enzymes acting in concert with cellobiohydrolases (CBHI and CBHII) from the same organism, indicating a highly effective enzymatic system for cellulose degradation. Controlled proteolysis with papain has allowed a so far unique cleavage of endoglucanases EG44 and EG38 into two domains: a core protein, which virtually lacks the capacity to absorb onto microcrystal-line cellulose but retains full catalytic activity against carboxymethyl cellulose and low molecular weight soluble substrates; and a peptide fragment corresponding to the cellulose binding domain. The latter appears to be of paramount significance in the mechanisms involved in the hydrolysis of microcrystalline cellulose.
Department of Biochemistry, University of Uppsala, Sweden.
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Uzcategui
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Johansson
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Ek
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Pettersson
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001487:Basidiomycota / Q000201:enzymology*; D002480:Cellulase / Q000032:analysis*; D002482:Cellulose / Q000378:metabolism*; D008969:Molecular Sequence Data; D014242:Trichoderma / Q000201:enzymology
D000596:Amino Acids; D002482:Cellulose; D002480:Cellulase