The MaxDiscovery™ Human Leptin ELISA Test Kit is designed for quantitative determination of the concentration of human leptin in serum, plasma, and cell culture supernatant. Human leptin is a 16 kDa polypeptide of 146 amino acid (aa) residues. It was originally identified using genetic mapping to locate a mutation that caused obesity in mice and eventually isolating the protein encoded by that gene. Named leptin (from leptos, Greek for thin) because of its ability to reduce fat stores, the protein shows high interspecies conservation, with mature human leptin being 87% and 84% identical to mouse and rat leptin proteins, respectively. Leptin is frequently referred to as OB protein, the product of the ob (obese) gene. Human leptin has been found to be active in both the mouse and rat systems. The expression of Leptin is very limited and has been found only in adipocytes. A mutation in the ob gene has been found in mice, but not in humans. This mutation results in a mature, non-functional, 81 aa residue, truncated leptin that contributes to the general obesity associated with the ob/ob mouse phenotype.