Catalyzes the C-C bond cleavage of fatty acid linked to acyl carrier protein (ACP) to generate pimelic acid for biotin biosynthesis. It has high affinity for long-chain fatty acids with the greatest affinity for myristic acid. a C2-C8-saturated long-chain fatty acyl-[ACP] + 3 O2 + 2 reduced [flavodoxin] = 6-carboxyhexanoyl-[ACP] + a fatty aldehyde + 3 H(+) + 3 H2O + 2 oxidized [flavodoxin] Binds 1 heme group covalently per subunit. Cofactor biosynthesis; biotin biosynthesis. Belongs to the cytochrome P450 family.