Catalyzes the transfer of endogenously produced octanoic acid from octanoyl-acyl-carrier-protein onto the lipoyl domains of lipoate-dependent enzymes, which catalyze essential redox reactions (PubMed:28757203). Lipoyl-ACP can also act as a substrate although octanoyl-ACP is likely to be the physiological substrate (By similarity). L-lysyl-[protein] + octanoyl-[ACP] = H(+) + holo-[ACP] + N(6)-octanoyl-L-lysyl-[protein] Protein modification; protein lipoylation via endogenous pathway; protein N(6)-(lipoyl)lysine from octanoyl-[acyl-carrier-protein]: step 1/2. The disease is caused by variants affecting the gene represented in this entry. In the reaction, the free carboxyl group of octanoic acid is attached via an amide linkage to the epsilon-amino group of a specific lysine residue of lipoyl domains of lipoate-dependent enzymes. Belongs to the LipB family.