Gla-Type Osteocalcin EIA Kit

Description:

Osteocalcin (OC), also known as γ-carboxyglutamic acid protein, is a small (5.9 kDa), vitamin K-dependent, hydroxyapatite (Ca²⁺)-binding protein synthesized exclusively by osteoblasts and odontoblasts. This tissue-specific expression of OC makes it an excellent indicator of overall cell activity for bone formation. Three γ-carboxyglutamic acid (Gla) residues at positions 17, 21, and 24 of the protein are responsible for binding calcium. Calcium-binding is, in turn, required for such biological activities as activation of the blood coagulation cascade. Thus, Gla-OC likely represents the active form of the protein, while Glu-OC, which has weak binding affinity to hydroxyapatite, represents the inactive form. Serum OC levels correlate well with bone formation rates and, thus, enzyme immunoassay (EIA) measurements of carboxylated OC (Gla-OC) vs. decarboxylated OC (Glu-OC) can be used for clinical evaluation studies. EIA systems may provide better leads of clinical information than do the conventional assays which cannot differentiate between active and inactive forms.

The Gla-Type Osteocalcin EIA Kit is a 96-well in vitro enzyme immunoassay kit for quantitative determination of human Gla-OC in serum, cultured cell extracts, cell culture supernatants, and other biological fluids. It is a solid phase sandwich EIA that utilizes two mouse monoclonal Gla-OC antibodies (one of which is coated on the plate, and the other is POD-labeled) for detection of carboxylated osteocalcin using a two-step incubation method. In the first step, samples are incubated in the antibody-coated microtiter plate. During the second step, the plate is washed and incubated with the POD-labeled Gla-OC antibody. A substrate is added, and the reaction between POD and the substrate (H2O2, TMBZ) results in a color development. The amount of sample Gla-OC is determined by measuring absorbance using an EIA plate reader. Accurate Gla-OC sample concentrations can be determined by comparing their specific absorbances with the absorbance obtained for the Standard plotted on a standard curve.