Bifunctional enzyme that catalyzes two different reactions involved in the biotin biosynthesis. Catalyzes a mechanistically unusual reaction, the ATP-dependent insertion of CO2 between the N7 and N8 nitrogen atoms of 7,8-diaminopelargonic acid (DAPA) to form an ureido ring. Catalyzes the transfer of the alpha-amino group from S-adenosyl-L-methionine (SAM) to 7-keto-8-aminopelargonic acid (KAPA) to form 7,8-diaminopelargonic acid (DAPA). It is the only aminotransferase known to utilize SAM as an amino donor. (7R,8S)-7,8-diammoniononanoate + ATP + CO2 = (4R,5S)-dethiobiotin + ADP + 3 H(+) + phosphate (8S)-8-amino-7-oxononanoate + S-adenosyl-L-methionine = (7R,8S)-7,8-diammoniononanoate + S-adenosyl-4-methylsulfanyl-2-oxobutanoate Shoulder at 335 nm (at pH 7.5 and 30 degrees Celsius). kcat is 0.072 min(-1) for 7,8-diamino-pelargonic acid aminotransferase + dethiobiotin synthetase activities, and 1.85 min(-1) for 7,8-diamino-pelargonic acid aminotransferase activity only (at pH 7.5 and 30 degrees Celsius). Cofactor biosynthesis; biotin biosynthesis; biotin from 7,8-diaminononanoate: step 1/2. Cofactor biosynthesis; biotin biosynthesis; 7,8-diaminononanoate from 8-amino-7-oxononanoate (SAM route): step 1/1. Homodimer. Only the isoform BIO3-BIO1 is detected at protein level in mitochondria. Arrested embryos at the transition to cotyledon stages of development (PubMed:11779812, PubMed:17993549). Biotin depletion leading to lethality; this phenotype is rescued by exogenous supply of biotin (PubMed:12644697, PubMed:23031218). May be due to a competing acceptor splice site. May be due to a competing acceptor splice site. May be due to an intron retention. In the N-terminal section; belongs to the dethiobiotin synthetase family. In the C-terminal section; belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. BioA subfamily. Was originally thought to correspond to two different genes At5g57590 and At5g57600. Was originally thought to correspond to two different genes At5g57590 and At5g57600.