This gene encodes a member of the acyl-coenzyme A oxidase family. The encoded protein is localized to peroxisomes and is the first enzyme of the fatty acid beta-oxidation pathway, which catalyzes the desaturation of acyl-coenzyme A to 2-trans-enoyl-coenzyme A. Disruption of this gene results in microvesicular steatohepatitis, spontaneous peroxisome proliferation, and the eventual development of hepatocellular carcinomas. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Dec 2012]