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) (PubMed:1092681, PubMed:1092682). It is the only animotransferase known to utilize SAM as an amino donor (PubMed:1092681, PubMed:1092682). Complements a bioU deletion in Synechocystis PCC 6803 (PubMed:32042199). (8S)-8-amino-7-oxononanoate + S-adenosyl-L-methionine = (7R,8S)-7,8-diammoniononanoate + S-adenosyl-4-methylsulfanyl-2-oxobutanoate Inhibited by amiclenomycin. S-adenosyl-L-(2-hydroxy-4-methylthio)butyric acid and adenosine are competitive inhibitors with SAM and uncompetitive inhibitors with KAPA as substrates (PubMed:1092682). S-adenosyl-L-ethionine, adenine and 8-keto-7-aminopelargonic acid are non-competitive inhibitors with both substrates (PubMed:1092682). Cofactor biosynthesis; biotin biosynthesis; 7,8-diaminononanoate from 8-amino-7-oxononanoate (SAM route): step 1/1. Homodimer. Repressed by BirA. Loss of biotin synthesis. Catalysis proceeds by a classical ping-pong bi-bi reaction mechanism. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. BioA subfamily.