Dethiobiotin synthetase involved in the biotin biosynthesis pathway. (7R,8S)-7,8-diammoniononanoate + ATP + CO2 = (4R,5S)-dethiobiotin + ADP + 3 H(+) + phosphate Cofactor biosynthesis; biotin biosynthesis; biotin from 7,8-diaminononanoate: step 1/2. Belongs to the dethiobiotin synthetase family.