Mediates activation of long-chain fatty acids for both synthesis of cellular lipids, and degradation via beta-oxidation (PubMed:10373116, PubMed:26893370, PubMed:29739804). Probably by regulating lipid storage and catabolism, plays a role in neuronal function (PubMed:25409104). a long-chain fatty acid + ATP + CoA = a long-chain fatty acyl-CoA + AMP + diphosphate Adult neurodegeneration, with marked dilation of photoreceptor axons (PubMed:10373116, PubMed:26893370, PubMed:29739804). Results in degeneration of lamina and retina, defects in the fenestrated basement membrane and ommatidial disarray (PubMed:26893370, PubMed:29739804). The phenotype is exacerbated in constant light conditions and improves in total darkness (PubMed:29739804). Effects are probably due to elevated levels of very long chain fatty acids (VLCFAs) (PubMed:10373116, PubMed:29739804). Feeding the fly mutant with glyceryl trioleate oil or medium-chain fatty acids, blocks the accumulation of excess VLCFAs as well as development of the pathology (PubMed:10373116, PubMed:29739804). Results in altered neuronal function, including altered sleep rebound following sleep deprivation (PubMed:25409104). Simultaneous knockout of hll results in enhanced retinal degeneration and altered fatty acids metabolism (PubMed:26893370). Belongs to the ATP-dependent AMP-binding enzyme family. Bubblegum subfamily.