title: Transketolase from Leishmania mexicana has a dual subcellular localization.
abstract: Transketolase has been characterized in Leishmania mexicana. A gene encoding this enzyme was identified and cloned. The gene was expressed in Escherichia coli and the protein was purified and characterized. An apparent K(m) of 2.75 mM for ribose 5-phosphate was determined. X-ray crystallography was used to determine the three-dimensional structure of the enzyme to a resolution of 2.2 A (1 A identical with 0.1 nm). The C-terminus of the protein contains a type-1 peroxisome-targeting signal, suggestive of a possible glycosomal subcellular localization. Subcellular localization experiments performed with promastigote forms of the parasite revealed that the protein was predominantly cytosolic, although a significant component of the total activity was associated with the glycosomes. Transketolase is thus the first enzyme of the nonoxidative branch of the pentose phosphate pathway whose presence has been demonstrated in a peroxisome-like organelle.
authors.affiliation: Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Veitch
authors.forename: Dante A
authors.initials: DA
authors.lastname: Maugeri
authors.forename: Juan Jose
authors.initials: JJ
authors.lastname: Cazzulo
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lindqvist
authors.forename: Michael P
authors.initials: MP
authors.lastname: Barrett
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray / Q000379:methods; D016054:DNA, Protozoan / Q000235:genetics; D007894:Leishmania mexicana / Q000737:chemistry* / Q000201:enzymology* / Q000254:growth & development; D008830:Microbodies / Q000737:chemistry / Q000201:enzymology; D008969:Molecular Sequence Data; D020675:Peroxisomes / Q000737:chemistry / Q000201:enzymology; D021382:Protein Sorting Signals / Q000502:physiology; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014174:Transketolase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D016054:DNA, Protozoan; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D014174:Transketolase