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.
Uzcategui
E
E
Department of Biochemistry, University of Uppsala, Sweden.
Johansson
G
G
Ek
B
B
Pettersson
G
G
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