In enzymology, a dethiobiotin synthase (EC 6.3.3.3) is an enzyme that catalyzes the chemical reaction

ATP + 7,8-diaminononanoate + CO₂ ${\displaystyle \rightleftharpoons }$ ADP + phosphate + dethiobiotin

The 3 substrates of this enzyme are ATP, 7,8-diaminononanoate, and CO₂, whereas its 3 products are ADP, phosphate, and dethiobiotin.

This enzyme belongs to the family of ligases, specifically the cyclo-ligases, which form carbon-nitrogen bonds. The systematic name of this enzyme class is 7,8-diaminononanoate:carbon-dioxide cyclo-ligase (ADP-forming). This enzyme is also called desthiobiotin synthase. This enzyme participates in biotin metabolism.

As of late 2007, 14 structures have been solved for this class of enzymes, with PDB accession codes 1A82, 1BS1, 1BYI, 1DAD, 1DAE, 1DAF, 1DAG, 1DAH, 1DAI, 1DAK, 1DAM, 1DBS, 1DTS, and 2QMO.

• Krell K, Eisenberg MA (1970). "The purification and properties of dethiobiotin synthetase". J. Biol. Chem. 245 (24): 6558–66. doi:10.1016/S0021-9258(18)62570-0. PMID 4921568.
• Yang H-C; Tani Y; Ogata K (1970). "Synthesis of biotin vitamers from biotin diaminocarboxylic acid or 7,8-diaminopelargonic acid by a purified enzyme of Pseudomonas graveolens". Agric. Biol. Chem. 34 (11): 1748–1750. doi:10.1271/bbb1961.34.1748.