Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 61 (3), 959-65

Characterization and Substrate Specificity of an endo-beta-1,4-D-glucanase I (Avicelase I) From an Extracellular Multienzyme Complex of Bacillus Circulans

Affiliations

Characterization and Substrate Specificity of an endo-beta-1,4-D-glucanase I (Avicelase I) From an Extracellular Multienzyme Complex of Bacillus Circulans

C H Kim. Appl Environ Microbiol.

Abstract

An endo-1,4-beta-D-glucanase I (Avicelase I; EC 3.2.1.4) was purified to homogeneity from an extracellular celluloxylanosome of Bacillus circulans F-2. The purification in the presence of 6 M urea yielded homogeneous enzyme. The enzyme had a monomeric structure, its relative molecular mass being 75 kDa as determined by gel filtration and 82 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI was 5.4, and the N-terminal amino acid sequence was ASNIGGWVGGNESGFEFG. The optimal pH was 4.5, and the enzyme was stable at pH 4 to 10. The enzyme has a temperature optimum of 50 degrees C, it was stable at 55 degrees C for 46 h, and it retains approximately 20% of its activity after 30 min at 80 degrees C. It showed high-level activity towards carboxymethyl cellulose (CMC) as well as p-nitrophenyl-beta-D-cellobioside, 4-methylumbelliferyl cellobioside, xylan, Avicel, filter paper, and some cello-oligosaccharides. Km values for birch xylan, CMC, and Avicel were 4.8, 7.2, and 87.0 mg/ml, respectively, while Vmax values were 256, 210, and 8.6 mumol x min-1 x mg-1, respectively. Cellotetraose was preferentially cleaved into cellobiose (G2) plus G2, and cellopentaose was cleaved into G2 plus cellotriose (G3), while cellohexaose was cleaved into cellotetraose plus G2 and to a lesser extent G3 plus G3. G3 was not cleaved at all. G2 was the main product of Avicel hydrolysis. Xylotetraose (X4) and xylobiose (X2) were mainly produced by the enzyme hydrolysis of xylan. G2 inhibited the activity of carboxymethyl cellulase and Avicelase, whereas Mg2+ stimulated it. The enzyme was completely inactivated by Hg2+, and it was inhibited by a thiol-blocking reagent. Hydrolysis of CMC took place, with a rapid decrease in viscosity but a slow liberation of reducing sugars. On the basis of these results, it appeared that the cellulase should be regarded as endo-type cellulase, although it hydrolyzed Avicel.

Similar articles

See all similar articles

Cited by 6 articles

See all "Cited by" articles

References

    1. Nature. 1970 Aug 15;227(5259):680-5 - PubMed
    1. Eur J Biochem. 1973 Aug 1;37(1):21-30 - PubMed
    1. Proc Natl Acad Sci U S A. 1990 Mar;87(6):2192-5 - PubMed
    1. Can J Microbiol. 1981 May;27(5):517-30 - PubMed
    1. J Bacteriol. 1990 Oct;172(10):6098-105 - PubMed
Feedback