Anti-SPAAR antibodies are used in the immunodetection of the protein small regulatory polypeptide of amino acid response. In humans, the canonical protein has a reported length of 90 amino acid residues and a mass of 9.6 kDa. Its subcellular localization is in the lysosomes. It is reported to be highly expressed in the lung, heart and skeletal muscle. Synonyms for this target antigen include long intergenic non-protein coding RNA 961 and small regulatory polypeptide of amino acids response. SPAAR gene orthologs have been reported in the mouse, rat and bovine species.