Bone formation and resorption requires the action of osteoblasts, which produce osteocalcin exclusively. Osteocalcin is typically produced with all three of its glutamate residues carboxylated (Gla-OC), affording the protein the ability to form a calcium pocket and bind bone matrix. The carboxylated glutamate residues are at positions 17, 21 and 24 of the protein. During bone metabolism, osteocalcin is released from bone matrix through the action of various enzymes, including one produced by osteoclasts. Most of the three glutamate residues are decarboxylated on osteocalcin (Glu-OC) when it is released into bloodstream from bone. Thus, osteocalcin is present in blood in both its Gla and Glu forms.
Osteocalcin, which contains 2-3 gamma-carboxyglutamate (Gla) residues and has a molecular weight of approximately 5.9 kDa, is known as a vitamin K-dependent calcium-binding non-collagenous protein. Produced only by osteoblasts, osteocalcin has been used as a unique marker of bone formation and resorption. The rat osteocalcin protein consists of 50 amino acids while human, bovine, rabbit and other species express an osteocalcin protein containing 49 amino acids. Osteocalcin is also a hormone that plays a role in insulin regulation and male fertility. Meanwhile, the undercarboxylated form of osteocalcin (ucOC) is responsible for glucose metabolism. The Gla-osteocalcin and Glu-osteocalcin ELISA kits enable researchers to study the roles of both carboxylated and undercarboxylated osteocalcin in metabolic disease, male fertility and bone formation and resorption.
The Rat Gla-Osteocalcin High Sensitive EIA Kit (Cat #MK126) is a 96-well format sandwich-type EIA that takes advantage of a C-terminal rat osteocalcin monoclonal antibody to capture osteocalcin (OC) in rat biological samples. This antibody has minimal cross-reactivity to bovine, human and rabbit osteocalcin. An enzyme-labeled antibody (Gla-OC4-30) specific to Gla-OC is used as the detection antibody, allowing this kit to detect Gla-osteocalcin with very high sensitivity. As such, this EIA kit is sensitive enough to pick up even minute traces of rat Gla-osteocalcin in cell supernatants supplemented with fetal calf serum.
The Rat Glu-Osteocalcin High Sensitive EIA Kit (Cat.# MK146) is a 96-well format sandwich-type EIA that uses a C-terminal rat osteocalcin monoclonal antibody to capture ostecalcin (OC). The kit's detection antibody specifically recognizes the glutamate residues present at positions 21 and 24 of the protein, making highly sensitive yet reproducible measurements of low level Glu-OC possible. Moreover, because both the Rat Gla-Osteocalcin High Sensitive EIA Kit (Cat.#MK126) and the Rat Glu-Osteocalcin High Sensitive EIA Kit (Cat.# MK146) contain the same capture antibody, both kits may be used for Gla/Glu detection (Cat.# MK147), making simultaneous monitoring of bone formation and resorption possible.