Involved in the first step of peroxisomal beta-oxidation by catalyzing the desaturation of fatty acid-derived side chains of ascaroside pheromones, which regulates development and behavior (PubMed:25775534, PubMed:27551084). Specifically, shortens ascarosides with 5-carbon omega side chain (asc-omega-C5) (PubMed:25775534, PubMed:27551084). Does not shorten indol-3-carbonyl(IC)-ascaroside with 7-carbon or 9-carbon side chains (PubMed:29863473). Does not catalyze the desaturation of fatty acids or hydroxylated fatty acids (PubMed:25775534, PubMed:27551084). asc-omegaC5-CoA + O2 = asc-omegaDeltaC5-CoA + H2O2 Activated by ATP (PubMed:27551084). ATP binding leads to a conformational change that promotes FAD cofactor binding and enzyme activity (PubMed:27551084). ATP binding likely occurs during acox-1.2 folding and/or dimer formation (PubMed:27551084). The preference for processing substrates with shorter fatty acid chains is likely due to the closed conformation of the active site (PubMed:27551084). kcat is 364 sec(-1) with asc-omega-C5-CoA (at 30 degrees Celsius and pH 7.4) (PubMed:25775534). kcat is 478 sec(-1) with asc-omega-C5-CoA (at 30 degrees Celsius, pH 7.4 and in complex with acox-1.1) (PubMed:25775534). Lipid metabolism; peroxisomal fatty acid beta-oxidation. Homodimer (Probable) (PubMed:27551084). Forms a heterodimer with acox-1.1 (PubMed:25775534). Induced by high temperatures (25 degrees Celsius) (PubMed:25775534). Down-regulated in dauer conditions (PubMed:25775534). Belongs to the acyl-CoA oxidase family.