Amornrat AroonnualTakuya NihiraTatsuji SekiWatanalai PanbangredMahidol UniversityOsaka University2018-08-242018-08-242007-04-03Enzyme and Microbial Technology. Vol.40, No.5 (2007), 1221-1227014102292-s2.0-33847758653https://repository.li.mahidol.ac.th/handle/20.500.14594/24212The gene encoding sucrose isomerase (palI NK33) was cloned from Klebsiella pneumoniae strain NK33-98-8. The gene was over-expressed in Escherichia coli BL21 (DE3) pLysS and its enzyme product (PalI NK33) was purified and characterized. PalI NK33 converts sucrose to 76.8% palatinose, 21.2% trehalulose and 1% each of glucose and fructose. The purified PalI NK33 showed the very high specific activity at 2362 U/mg and Kmfor sucrose was 42.7 ± 0.75 mM (at pH 6.0 and 30 °C). The enzyme activity was completely inhibited by 1 mM concentration of either Hg2+or SDS. Ca2+, Li2+and Mg2+at 1 mM slightly enhanced enzyme activity. Mutations on Asp140, located within the conserved sequence region I to either glutamic acid, glycine or asparagine had drastically reduced enzyme activity. The change of amino acid residues in the sequence325RLDRD329to325RYDRA329reduced enzyme activity 24-fold and did not affect ratio of palatinose and trehalulose formation. © 2006 Elsevier Inc. All rights reserved.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyImmunology and MicrobiologyArticleSCOPUS10.1016/j.enzmictec.2006.09.011