Novel Substrate Specificity of D-Arabinose Isomerase from Klehsiella pneumoniae and Its Application to Production of D-Altrose from D-Psicose

摘要

D-Arabinose isomerase from Klebsiella pneumoniae 40bXX was purified 12-fold with a 62.5% yield indicated by its electrophoretic homogeneity.The purified enzyme showed the highest activities toward D-arabinose and L-fucose as substrates at optimum conditions (50 mM glycine- NaOH,pH 9.0,40 deg C).The enzyme had a broad range of substrate specificities toward various D/L-aldoses,i.e.,D-arabinose,L-fucose,D/L-xylose,D-mannose,D/L-lyxose,L-glucose,D-altrose and D/L-galactose.The equilibrium ratios between D-arabinose and D-ribulose,L-fucose and L-fucu-lose,D-altrose and D-psicose,and L-galactose and L-tagatose were 90:10,90:10,13:87 and 25:75,respectively.Using a combination of the immobilized D-tagatose 3-epimerase and D-arabinose isomerase,we achieved the production of D-altrose from D-fructose in a batch reactor.We successfully produced approximately 12 g of D-altrose from 200 g of D-fructose in a reaction series with an overall yield of 6%.The product obtained was confirmed to be D-altrose by HPLC and ~(13)C-NMR.To the best of our knowledge,this is the first report on the production of D-altrose from a cheap sugar,D-fructose,using an enzymatic method.