Biochemical and Genetic Analysis of 4-Hydroxypyridine Catabolism in <i>Arthrobacter</i> sp. Strain IN13
2020
Justas Vaitekūnas | Renata Gasparavičiūtė | Jonita Stankevičiūtė | Gintaras Urbelis | Rolandas Meškys
<i>N</i>-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 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.
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