Anti-kappa opioid receptor antibodies are protein reagents that detect specific antigens. The kappa opioid receptor antigen is another term for the human protein opioid receptor kappa 1, encoded by the OPRK1 gene. The protein is known to function in carbohydrate metabolism and homeostasis and the cellular response to lipopolysaccharides, among other biological roles. Canonically, it has an amino acid length of 380 residues and a mass of 42.6 kilodaltons. Its subcellular localization is in the cell membrane and it is notably expressed in the brain and placenta. The kappa opioid receptor protein is a member of the G-protein coupled receptor 1 protein family. Other alias names for kappa opioid receptor include K-OR-1, KOP, and KOR.