Functional Identification of Putrescine C- and N-Hydroxylases.

Abstract

The small polyamine putrescine (1,4-diaminobutane) is ubiquitously and abundantly found in all three domains of life. It is a precursor, through N-aminopropylation or N-aminobutylation, for biosynthesis of the longer polyamines spermidine, sym-homospermidine, spermine, and thermospermine and longer and branched chain polyamines. Putrescine is also biochemically modified for purposes of metabolic regulation and catabolism, e.g. N-acetylation and N-glutamylation, and for incorporation into specialized metabolites, e.g. N-methylation, N-citrylation, N-palmitoylation, N-hydroxylation, and N-hydroxycinnamoylation. Only one example is known where putrescine is modified on a methylene carbon: the formation of 2-hydroxyputrescine by an unknown C-hydroxylase. Here, we report the functional identification of a previously undescribed putrescine 2-hydroxylase, a Rieske-type nonheme iron sulfur protein from the β-proteobacteria Bordetella bronchiseptica and Ralstonia solanacearum. Identification of the putrescine 2-hydroxylase will facilitate investigation of the physiological functions of 2-hydroxyputrescine. One known role of 2-hydroxyputrescine has direct biomedical relevance: its role in the biosynthesis of the cyclic hydroxamate siderophore alcaligin, a potential virulence factor of the causative agent of whooping cough, Bordetella pertussis. We also report the functional identification of a putrescine N-hydroxylase from the γ-proteobacterium Shewanella oneidensis, which is homologous to FAD- and NADPH-dependent ornithine and lysine N-monooxygenases involved in siderophore biosynthesis. Heterologous expression of the putrescine N-hydroxylase in E. coli produced free N-hydroxyputrescine, never detected previously in a biological system. Furthermore, the putrescine C- and N-hydroxylases identified here could contribute new functionality to polyamine structural scaffolds, including C-H bond functionalization in synthetic biology strategies.

Cite this paper

@article{Li2016FunctionalIO, title={Functional Identification of Putrescine C- and N-Hydroxylases.}, author={Bin Li and Tiffany M. Lowe-Power and Shin Kurihara and Stephen Gonzales and Jacinth Naidoo and John B MacMillan and Caitilyn Allen and Anthony Michael}, journal={ACS chemical biology}, year={2016}, volume={11 10}, pages={2782-2789} }