The prodrug activator EtaA from Mycobacterium tuberculosis is a Baeyer-Villiger monooxygenase.
EtaA is a newly identified FAD-containing monooxygenase that is responsible for activation of several thioamide prodrugs in Mycobacterium tuberculosis. It was found that purified EtaA displays a remarkably low activity with the antitubercular prodrug ethionamide. Hinted by the presence of a Baeyer-Villiger monooxygenase sequence motif in the EtaA sequence, we have been able to identify a large number of novel EtaA substrates. It was discovered that the enzyme converts a wide range of ketones to the corresponding esters or lactones via a Baeyer-Villiger reaction, indicating that EtaA represents a Baeyer-Villiger monooxygenase. With the exception of aromatic ketones (phenylacetone and benzylacetone), long-chain ketones (e.g. 2-hexanone and 2-dodecanone) also are converted. EtaA is also able to catalyze enantioselective sulfoxidation of methyl-p-tolylsulfide. Conversion of all of the identified substrates is relatively slow with typical k(cat) values of around 0.02 s(-1). The best substrate identified so far is phenylacetone (K(m) = 61 microM, k(cat) = 0.017 s(-1)). Redox monitoring of the flavin cofactor during turnover of phenylacetone indicates that a step in the reductive half-reaction is limiting the rate of catalysis. Intriguingly, EtaA activity could be increased by one order of magnitude by adding bovine serum albumin. This reactivity and substrate acceptance-profiling study provides valuable information concerning this newly identified prodrug activator from M. tuberculosis.
Fraaije
Marco W
MW
Laboratory of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. m.w.fraaije@chem.rug.av.nl
Kamerbeek
Nanne M
NM
Heidekamp
Annelies J
AJ
Fortin
Riccardo
R
Janssen
Dick B
DB
D000096:Acetone / Q000031:analogs & derivatives* / Q000737:chemistry; D020816:Amino Acid Motifs; D000995:Antitubercular Agents / Q000494:pharmacology; D001426:Bacterial Proteins; D002384:Catalysis; D004305:Dose-Response Relationship, Drug; D004952:Esters / Q000737:chemistry; D005000:Ethionamide / Q000494:pharmacology*; D007659:Ketones / Q000737:chemistry; D007700:Kinetics; D007783:Lactones; D008956:Models, Chemical; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010105:Oxygenases / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology*; D011355:Prodrugs / Q000737:chemistry*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D012709:Serum Albumin / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors
D000995:Antitubercular Agents; D001426:Bacterial Proteins; D004952:Esters; D007659:Ketones; D007783:Lactones; D011355:Prodrugs; D011994:Recombinant Proteins; D012709:Serum Albumin; C414178:etaA protein, Mycobacterium tuberculosis; D000096:Acetone; D010105:Oxygenases; C008863:1-phenyl-2-propanone; D005000:Ethionamide; D010100:Oxygen