title: Identification, expression, and characterization of the highly conserved D-xylose isomerase in animals.
abstract: D-xylose is a necessary sugar for animals. The xylanase from a mollusk, Ampullaria crossean, was previously reported by our laboratory. This xylanase can degrade the xylan into D-xylose. But there is still a gap in our knowledge on its metabolic pathway. The question is how does the xylose enter the pentose pathway? With the help of genomic databases and bioinformatic tools, we found that some animals, such as bacteria, have a highly conserved D-xylose isomerase (EC 5.3.1.5). The xylose isomerase from a sea squirt, Ciona intestinali, was heterogeneously expressed in Escherichia coli and purified to confirm its function. The recombinant enzyme had good thermal stability in the presence of Mg(2+). At the optimum temperature and optimum pH environment, its specific activity on D-xylose was 0.331 micromol/mg/min. This enzyme exists broadly in many animals, but it disappeared in the genome of Amphibia-like Xenopus laevis. Its sequence was highly conserved. The xylose isomerases from animals are very interesting proteins for the study of evolution.
authors.affiliation: Key Laboratory of Proteomics, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China. fkzhao@sibs.ac.cn
authors.forename: Ming
authors.initials: M
authors.lastname: Ding
authors.forename: Yigang
authors.initials: Y
authors.lastname: Teng
authors.forename: Qiuyu
authors.initials: Q
authors.lastname: Yin
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Fukun
authors.initials: F
authors.lastname: Zhao
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002938:Ciona intestinalis / Q000201:enzymology / Q000235:genetics; D017124:Conserved Sequence; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D005091:Exons; D007438:Introns; D008969:Molecular Sequence Data; D010427:Pentose Phosphate Pathway; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism; D014994:Xylose / Q000737:chemistry / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D014994:Xylose; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase