Catalyzes the conversion of long-chain fatty acids to their active form acyl-CoA for both synthesis of cellular lipids, and degradation via beta-oxidation (PubMed:22633490, PubMed:24269233). Plays an important role in fatty acid metabolism in brain and the acyl- CoAs produced may be utilized exclusively for the synthesis of the brain lipid. {ECO:0000269|PubMed:22633490, ECO:0000269|PubMed:24269233}. This is the function of ACSL6 (acyl-CoA synthetase long chain family member 6, ENSG00000164398).