Authors: Anjali Madhavan Sriappareddy Tamalampudi Kazunari Ushida Daisuke Kanai Satoshi Katahira Aradhana Srivastava Hideki Fukuda Virendra S Bisaria Akihiko Kondo
Publish Date: 2008/12/03
Volume: 82, Issue: 6, Pages: 1067-
Abstract
The cDNA sequence of the gene for xylose isomerase from the rumen fungus Orpinomyces was elucidated by rapid amplification of cDNA ends The 1314nucleotide gene was cloned and expressed constitutively in Saccharomyces cerevisiae The deduced polypeptide sequence encoded a protein of 437 amino acids which showed the highest similarity to the family II xylose isomerases Further characterization revealed that the recombinant enzyme was a homodimer with a subunit of molecular mass 49 kDa Cell extract of the recombinant strain exhibited high specific xylose isomerase activity The pH optimum of the enzyme was 75 while the low temperature optimum at 37°C was the property that differed significantly from the majority of the reported thermophilic xylose isomerases In addition to the xylose isomerase gene the overexpression of the S cerevisiae endogenous xylulokinase gene and the Pichia stipitis SUT1 gene for sugar transporter in the recombinant yeast facilitated the efficient production of ethanol from xylose
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