| Summary: | <b><i> </i></b>N-Heterocyclic compounds are widely spread in the biosphere, being constituents of alkaloids, cofactors, allelochemicals, and artificial substances. However, the fate of such compounds including a catabolism of hydroxylated pyridines is not yet fully understood. <i>Arthrobacter </i>sp. IN13 is capable of using 4-hydroxypyridine as a sole source of carbon and energy. Three substrate-inducible proteins were detected by comparing protein expression profiles, and peptide mass fingerprinting was performed using MS/MS. After partial sequencing of the genome, we were able to locate genes encoding 4-hydroxypyridine-inducible proteins and identify the <i>kpi </i>gene cluster consisting of 16 open reading frames. The recombinant expression of genes from this locus in <i>Escherichia</i> <i>coli</i> and <i>Rhodococcus erytropolis </i>SQ1 allowed an elucidation of the biochemical functions of the proteins. We report that in <i>Arthrobacter </i>sp. IN13, the initial hydroxylation of 4-hydroxypyridine is catalyzed by a flavin-dependent monooxygenase (KpiA). A product of the monooxygenase reaction is identified as 3,4-dihydroxypyridine, and a subsequent oxidative opening of the ring is performed by a hypothetical amidohydrolase (KpiC). The 3-(<i>N</i>-formyl)-formiminopyruvate formed in this reaction is further converted by KpiB hydrolase to 3-formylpyruvate. Thus, the degradation of 4-hydroxypyridine in <i>Arthrobacter </i>sp. IN13 was analyzed at genetic and biochemical levels, elucidating this catabolic pathway.
|
|---|
