Klotho beta (KLB) is a 130-kDA type I transmembrane protein composed of a signal sequence, a 29 aa intracellular domain, and two extracellular glycosidase domains. KLB functions as an essential co-receptor of fibroblast growth factor receptor complexes, like FGFR1c and FGFr4, thereby facilitating the activation of downstream signaling in bile acid synthesis. Its gene located on chromosome 4p14, KLB is selectively abundant in metabolic tissues (adipose, liver, pancreas) and is essential for high-affinity binding of endocrine FGF19 and FGF21 involved in homeostatic glucose metabolism and energy expenditure. Mutation is associated with metabolic defects such as hypogonadotropic hypogonadism. KLB overexpression promotes the activation of the PI3K/AKT signaling pathway stimulated by TGF-β1 and thus enhances cell fibrosis and proliferation in patients with intrauterine adhesion. KLB upregulation in prostate cancer (via Rab8a-dependent mechanism) and hepatocellular carcinoma tissues shows a potential tumor-promoting role.

≥ 95 % as determined by SDS-PAGE. ≥ 95 % as determined by SEC-HPLC.