In vitro characterization of a nitro-forming oxygenase involved in 3-(trans-2’-aminocyclopropyl)alanine biosynthesis

In vitro characterization experiments revealed the formations of 3-( trans -2’-aminocyclopropyl)alanine ((3-Acp)Ala) and 3-( trans -2’-nitrocyclopropyl)alanine ((3-Ncp)Ala) are originated via two homologous proteins, BelK and HrmI, which regioselectively catalyze the Nε-oxygenation of l -lysine. The two enzymes belong to the emerging heme-oxygenase-like diiron oxidase and oxygenase (HDO) superfamily and the catalytic center of BelK is validated by homology modeling and site-directed mutations. Based on the in vitro characterization, the biosynthetic pathways of (3-Acp)Ala and (3-Ncp)Ala are proposed. Herein, we report that the N-oxygenases, BelK and HrmI, catalyze the Nε-oxygenation of l -lysine and initiate the biosyntheses of l -(3-Acp)Ala and l -(3-Ncp)Ala.