Purification, properties and mass spectrometry analysis of two novel thermotolerant endoglucanases from Bacillus akibai Ⅰ-2

摘要

The alkaliphilic bacterium strain Ⅰ-2,which was isolated from soda lakes,was identified as Bacillus akibai by 16S rRNA sequence analysis and suggested to be a new subspecies of genus Bacillus.Two novel thermotolerant alkaline endoglucanases Ⅰ-2-A and Ⅰ-2-B were produced by this alkaliphilic strain.The purified Ⅰ-2-A and Ⅰ-2-B had molecular mass of approximately 60 and 90 kDa,respectively.The optimum pH of Ⅰ-2-A was about 9.0,while that of Ⅰ-2-B was about 8.0.Both enzymes exhibited maximum activity at around 50 °C and were stable up to 50 °C.The two enzymes were resistant to most metal ions and reagents examined.Mass spectrometry analysis indicated that Ⅰ-2-A was probably different from the endoglucanases reported.Ⅰ-2-B showed homology with those of family A5 endoglucanases but low similarity was found in C-terminal amino acid sequence.