Involved in the first step of peroxisomal beta-oxidation by catalyzing the desaturation of fatty acid-derived side chains (PubMed:25775534, PubMed:29537254, PubMed:27551084). Specifically, catalyzes the desaturation of fatty acids heptanoyl-CoA (C7), nonanoyl-CoA (C9), dodecanoyl-CoA (C12) and to a lesser extent pentanoyl-CoA (C5) and hexadecanoyl-CoA (C16), and hydroxylated fatty acid hydroxynonanoyl-CoA (PubMed:25775534, PubMed:29537254, PubMed:27551084). Also, catalyzes the desaturation fatty acid-derived side chains of ascaroside pheromones, which regulates development and behavior (PubMed:20610393, PubMed:25775534, PubMed:29537254, PubMed:29863473, PubMed:27551084). Specifically, shortens ascaroside with 5-carbon omega side chain (asc-omega-C5), 7-carbon side chain (asc-C7), 9-carbon side chain (asc-C9), 11-carbon side chain (asc-C11), 13-carbon side chain (asc-C13), 15-carbon side chain (asc-C15) and to a lesser extent ascarosides with 7-omega-carbon side chain (asc-omega-C7) (PubMed:25775534, PubMed:29537254, PubMed:27551084). Also shortens indol-3-carbonyl(IC)-ascarosides with 7-carbon side chain (IC-asc-C7) and to a lesser extent (IC)-ascarosides with 9-carbon side chain (IC-asc-C9) (PubMed:29863473). May associate and regulate the folding and/or the catalytic activity of other acyl-coenzyme A oxidases including acox-1.2, acox-1.3, acox-1.4 and acox-3 modulating the type of ascarosides produced (PubMed:25775534, PubMed:29537254, PubMed:29863473). In association with acox-1.3, catalyzes the desaturation of asc-C7-CoA but not of fatty acids or hydroxylated fatty acids (PubMed:25775534). Involved in the biosynthesis of asc-C6-MK (daumone 2) and asc-delta-C9 (daumone 3) but not asc-C7 (daumone 1); daumones are pheromones produced during unfavourable growth conditions which promote entry into the dauer stage (PubMed:20610393). nonanoyl-CoA + O2 = (2E)-nonenoyl-CoA + H2O2 dodecanoyl-CoA + O2 = (2E)-dodecenoyl-CoA + H2O2 a 2,3-saturated acyl-CoA + O2 = a (2E)-enoyl-CoA + H2O2 heptanoyl-CoA + O2 = (2E)-heptenoyl-CoA + H2O2 (8R)-8-hydroxynonanoyl-CoA + O2 = (2E,8R)-8-hydroxynonenoyl-CoA + H2O2 O2 + pentanoyl-CoA = (2E)-pentenoyl-CoA + H2O2 hexadecanoyl-CoA + O2 = (2E)-hexadecenoyl-CoA + H2O2 IC-asc-C7-CoA + O2 = H2O2 + IC-asc-DeltaC7-CoA IC-asc-C9-CoA + O2 = H2O2 + IC-asc-DeltaC9-CoA asc-omegaC5-CoA + O2 = asc-omegaDeltaC5-CoA + H2O2 asc-C7-CoA + O2 = asc-DeltaC7-CoA + H2O2 asc-omegaC7-CoA + O2 = asc-omegaDeltaC7-CoA + H2O2 asc-C9-CoA + O2 = asc-DeltaC9-CoA + H2O2 asc-C13-CoA + O2 = asc-DeltaC13-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-1.1 folding and/or dimer formation (PubMed:27551084). kcat is 252 sec(-1) with asc-C9-CoA (at 30 degrees Celsius and pH 7.4) (PubMed:25775534). kcat is 144 sec(-1) with asc-C7-CoA (at 30 degrees Celsius, pH 7.4 and in complex with acox-1.3) (PubMed:25775534). kcat is 478 sec(-1) with asc-omega-C5-CoA (at 30 degrees Celsius, pH 7.4 and in complex with acox-1.2) (PubMed:25775534). Lipid metabolism; peroxisomal fatty acid beta-oxidation. Homodimer (Probable). Forms a heterodimer with acox-1.2 (PubMed:25775534). Forms a heterodimer with acox-1.3; the interaction may be important for the stability of acox-1.3 (PubMed:25775534). Expressed in hypodermis and intestine. Induced by high temperatures (25 degrees Celsius). RNAi-mediated knockdown abolishes production of dauer pheromone daumone 2, severely reduces production of daumone 3 and increases production of daumone 1. Belongs to the acyl-CoA oxidase family.