A 'suicide' enzyme that participates in biotin synthesis. Catalyzes the formation of (S)-8-amino-7-oxononanoate (DAN-carbamic acid) from (7R,8S)-8-amino-7-(carboxyamino)nonanoate (DAN), a function equivalent to the cannonical BioA reaction and the first half-reaction of BioD. The cellular requirement for biotin is thought be low enough that this single turnover enzyme supplies a sufficient amount of the cofactor. Overall it catalyzes three reactions: formation of a covalent linkage with 8-amino-7-oxononanoate to yield a BioU-DAN conjugate at the epsilon-amino group of Lys124 of BioU using NAD(P)H, carboxylation of the conjugate to form BioU-DAN-carbamic acid, and release of DAN-carbamic acid using NAD(P)+ (By similarity) (PubMed:32042199). A coupled Synechocystis BioU/BioD assay produces dethiobiotin from DAN. Complements a bioA deletion in E.coli but not a bioD1 deletion (PubMed:32042199). (8S)-8-amino-7-oxononanoate + CO2 + L-lysyl-[protein] = (7R,8S)-8-amino-7-(carboxyamino)nonanoate + (S)-2-amino-6-oxohexanoyl-[protein] + 2 H(+) (8S)-8-amino-7-oxononanoate + H(+) + L-lysyl-[protein] + NADPH = H2O + N(6)-[(2S,3R)-2-amino-8-carboxyoctan-3-yl]-L-lysyl-[protein] + NADP(+) CO2 + H2O + N(6)-[(2S,3R)-2-amino-8-carboxyoctan-3-yl]-L-lysyl-[protein] + NADP(+) = (7R,8S)-8-amino-7-(carboxyamino)nonanoate + (S)-2-amino-6-oxohexanoyl-[protein] + 3 H(+) + NADPH (8S)-8-amino-7-oxononanoate + H(+) + L-lysyl-[protein] + NADH = H2O + N(6)-[(2S,3R)-2-amino-8-carboxyoctan-3-yl]-L-lysyl-[protein] + NAD(+) CO2 + H2O + N(6)-[(2S,3R)-2-amino-8-carboxyoctan-3-yl]-L-lysyl-[protein] + NAD(+) = (7R,8S)-8-amino-7-(carboxyamino)nonanoate + (S)-2-amino-6-oxohexanoyl-[protein] + 3 H(+) + NADH Cofactor biosynthesis; biotin biosynthesis. Monomer. Has 2 domains; discontinuous domain I (residues 1-149 and 291-331) forms a nucleotide-binding domain while domain II (residues 150-290) binds substrate. For native protein. For 7,8-diaminononanoate acid-protein (DAN) conjugate, a reaction intermediate. Loss of biotin biosynthesis. In canonical biotin synthesis a pimeloyl-conjugate is transformed into biotin by the subsequent action of BioF, BioA, BioD and BioB. This enzyme replaces BioA and performs the first half-reaction of BioD. In Synechocystis BioD acts on the product of this enzyme. Belongs to the BioU family.