title: The 3-ureidopropionase of Caenorhabditis elegans, an enzyme involved in pyrimidine degradation.
abstract: Pyrimidines are important metabolites in all cells. Levels of cellular pyrimidines are controlled by multiple mechanisms, with one of these comprising the reductive degradation pathway. In the model invertebrate Caenorhabditis elegans, two of the three enzymes of reductive pyrimidine degradation have previously been characterized. The enzyme catalysing the final step of pyrimidine breakdown, 3-ureidopropionase (β-alanine synthase), had only been identified based on homology. We therefore cloned and functionally expressed the 3-ureidopropionase of C. elegans as hexahistidine fusion protein. The purified recombinant enzyme readily converted the two pyrimidine degradation products: 3-ureidopropionate and 2-methyl-3-ureidopropionate. The enzyme showed a broad pH optimum between pH 7.0 and 8.0. Activity was highest at approximately 40 °C, although the half-life of activity was only 65 s at that temperature. The enzyme showed clear Michaelis-Menten kinetics, with a K(m) of 147 ± 26 μM and a V(max) of 1.1 ± 0.1 U·mg protein(-1). The quaternary structure of the recombinant enzyme was shown to correspond to a dodecamer by 'blue native' gel electrophoresis and gel filtration. The organ specific and subcellular localization of the enzyme was determined using a translational fusion to green fluorescent protein and high expression was observed in striated muscle cells. With the characterization of the 3-ureidopropionase, the reductive pyrimidine degradation pathway in C. elegans has been functionally characterized.
authors.affiliation: Institut für Zoophysiologie, Westfälische Wilhelms-Universität, Münster, Germany. tim.janowitz@rub.de
authors.forename: Tim
authors.initials: T
authors.lastname: Janowitz
authors.forename: Irene
authors.initials: I
authors.lastname: Ajonina
authors.forename: Markus
authors.initials: M
authors.lastname: Perbandt
authors.forename: Christian
authors.initials: C
authors.lastname: Woltersdorf
authors.forename: Patrick
authors.initials: P
authors.lastname: Hertel
authors.forename: Eva
authors.initials: E
authors.lastname: Liebau
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gigengack
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D017931:DNA Primers; D004331:Drosophila melanogaster / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007700:Kinetics; D010802:Phylogeny; D014176:Protein Biosynthesis; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology
chemical_list: D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; D000581:Amidohydrolases; C021590:beta-ureidopropionase