Purification and characterization of two endoglucanases from Melanocarpus sp. MTCC 3922

This study reports the purification and characterization of endoglucanases (EG I and EG II) from a newly isolated thermophilic fungus, Melanocarpus sp. MTCC 3922. The molecular weight of EG I and EG II as with SDS-PAGE and pI were ∼40 and 50 kDa, and ∼4.0 and 3.6, respectively. EG I and EG II were optimally active at 50 and 70 °C, and pH 6.0 and 5.0, respectively. EG I was active over a broad range of pH (5.0–7.0), whereas, loss of activity was observed as the temperature was increased from 50 to 80 °C. However, EG II was active over pH 4.0–6.0 and temperature 40–80 °C. The presence of mercaptoethanol and SDS inhibited the EG I activity but showed no negative effect on EG II. Both the endoglucanases showed higher activity against barley-β-glucan as compared to CMC. Km values of EG I and EG II for barley-β-glucan were lower than CMC. Turn over number (Kcat) and catalytic efficiency (Kcat/Km) values of both the endoglucanases were higher with barley-β-glucan as substrate than CMC. EG I showed affinity for Avicel indicating the presence of cellulose binding domains (CBD) whereas, EG II was found to lack CBD.