Description(s):
Cathepsin D (CTSD) is an aspartic protease that is found in lysosomes. The primary function of this proteinase is to degrade proteins and activate precursors of bioactive proteins. Over expression of CTSD has been found to stimulate tumorigenicity and metastasis. Furthermore, mutations in the CTSD gene have been linked to several diseases, including breast cancer and Alzheimer disease. CTSD is clinically significant because it is an indicator of poor prognosis in breast cancer patients.
Principle
The wells of the plate are coated with capture antibody specific to CTSD. In this assay, the test sample initially reacts with the solid phase capture antibody, resulting in CTSD being bound to the well. The wells are then washed to remove unbound proteins, and biotin-linked antibodies are added to bind to the immobilized CTSD. After washing away the unbound antibodies, Streptavidin-HRP conjugate is added to form a complex with the antibody-bound CTSD. After incubation, the wells are washed to remove unbound Streptavidin-HRP conjugate. TMB substrate is then added and forms a blue color when the HRP-linked antibodies are detected. The reaction is then terminated with Stop Solution, which changes the color from blue to yellow. The CTSD concentration in each well is directly proportional to its color intensity and can be quantified by measuring its optical density at 450 nm (OD450) in a microplate reader.
