Abstract
This study reports purification and characterization of two catalytically distinct endoglucanases (EGI and EGII) from a thermotolerant fungus Aspergillus nidulans. The endoglucanases (EGI and EGII) exhibited molecular masses of 56 and 31 kDa and pIs of 3.6 and 3.8, respectively. EGI was putatively classified as GH7 family member catalyzed carboxymethyl cellulose, xyloglucan, barley β-glucan as well as pNP-β-D-lactopyranoside and pNP-cellobioside, and was optimally active at 50°C and pH 4.0. Whereas, EGII lacking CBD preferentially recognized barley β-glucan when compared substrate CMC, xyloglucan and lichenan and was putatively classified as GH12 member. Interestingly, EGII was characterized to be thermoacidophilic exhibiting 96% its activity at pH 2.0 and at 60°C. Hydrolysis of barley β-glucan and CMC by EGI and EGII liberated cellobiose as a major product. HPLC analysis showed that barley β-glucan hydrolysate obtained by action of EGI showed high levels of glucose in addition to cellobiose indicating towards an exo type action of this enzyme.
Key words: Thermoacidophilic endoglucanases, GH7, GH12, barley β-glucan
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