Cloning and sequence of a type I pullulanase from an extremely thermophilic anaerobic bacterium, Caldicellulosiruptor saccharolyticus

摘要

A gene coding for a pullulanase from the obligately anaerobic, extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus has been cloned in Escherichia coli. It consists of an open reading frame (pulA) of 2478 bp which codes for an enzyme of 95 732 Da and is flanked by two other open reading frames. A truncated version of the gene which lacks 381 bp of 5′-sequence also has pullulanase activity and it appears that the amino-terminal portion of the gene is not essential for either activity or thermostability. Amino acid sequence comparisons with other published amylases and pullulanases showed that it possesses homology to the four key regions common to these enzymes.