title: Identification of a 5'-deoxyadenosine deaminase in Methanocaldococcus jannaschii and its possible role in recycling the radical S-adenosylmethionine enzyme reaction product 5'-deoxyadenosine.
abstract: We characterize here the MJ1541 gene product from Methanocaldococcus jannaschii, an enzyme that was annotated as a 5'-methylthioadenosine/S-adenosylhomocysteine deaminase (EC 3.5.4.31/3.5.4.28). The MJ1541 gene product catalyzes the conversion of 5'-deoxyadenosine to 5'-deoxyinosine as its major product but will also deaminate 5'-methylthioadenosine, S-adenosylhomocysteine, and adenosine to a small extent. On the basis of these findings, we are naming this new enzyme 5'-deoxyadenosine deaminase (DadD). The Km for 5'-deoxyadenosine was found to be 14.0 ± 1.2 μM with a kcat/Km of 9.1 × 10(9) M(-1) s(-1). Radical S-adenosylmethionine (SAM) enzymes account for nearly 2% of the M. jannaschii genome, where the major SAM derived products is 5'-deoxyadenosine. Since 5'-dA has been demonstrated to be an inhibitor of radical SAM enzymes; a pathway for removing this product must be present. We propose here that DadD is involved in the recycling of 5'-deoxyadenosine, whereupon the 5'-deoxyribose moiety of 5'-deoxyinosine is further metabolized to deoxyhexoses used for the biosynthesis of aromatic amino acids in methanogens.
authors.affiliation: Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Miller
authors.forename: Kaitlin
authors.initials: K
authors.lastname: O'Brien
authors.forename: Huimin
authors.initials: H
authors.lastname: Xu
authors.forename: Robert H
authors.initials: RH
authors.lastname: White
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003839:Deoxyadenosines / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019848:Gene Expression Regulation, Archaeal / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D063747:Methanocaldococcus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D009154:Mutation; D009709:Nucleotide Deaminases / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D003839:Deoxyadenosines; C033714:5'-deoxyadenosine; D012436:S-Adenosylmethionine; D009709:Nucleotide Deaminases