title: Identification and characterization of D-xylulokinase from the D-xylose-fermenting fungus, Mucor circinelloides.
abstract: D-Xylulokinase catalyzes the phosphorylation of D-xylulose in the final step of the pentose catabolic pathway to form d-xylulose-5-phosphate. The D-xylulokinase activity was found to be induced by both D-xylose and L-arabinose, as well as some of the other enzymes involved in the pentose catabolism, in the D-xylose-fermenting zygomycetous fungus, Mucor circinelloides NBRC 4572. The putative gene, xyl3, which may encode D-xylulokinase, was detected in the genome sequence of this strain. The amino acid sequence deduced from the gene was more similar to D-xylulokinases from an animal origin than from other fungi. The recombinant enzyme was purified from the E. coli transformant expressing xyl3 and then characterized. The ATP-dependent phosphorylative activity of the enzyme was the highest toward D-xylulose. Its kinetic parameters were determined as Km (D-xylulose) = 0.29 mM and Km (ATP) = 0.51 mM, indicating that the xyl3 gene encoded D-xylulokinase (McXK). Western blot analysis revealed that McXK was induced by L-arabinose as well as D-xylose and the induction was repressed in the presence of D-glucose, suggesting that the enzyme may be involved in the catabolism of D-xylose and L-arabinose and is subject to carbon catabolite repression in this fungus. This is the first study on D-xylulokinase from zygomycetous fungi.
authors.affiliation: Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, Imizu, Toyama, Japan.
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Komeda
authors.forename: Shino
authors.initials: S
authors.lastname: Yamasaki-Yashiki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hoshino
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Asano
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000235:genetics; D000431:Ethanol; D005285:Fermentation; D008969:Molecular Sequence Data; D009089:Mucor / Q000201:enzymology* / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D014994:Xylose / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D000431:Ethanol; D014994:Xylose; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase
keywords: Zygomycetes; pentose catabolism; pentose fermentation