A procollagen peptide contains an additional peptide sequence, termed the propeptide, at its amino- and carboxy terminal ends. Collagen types I, II, III, IV and V are synthesized as precursor molecules called procollagens. Propeptides facilitate the winding of procollagen molecules into a triple-helix conformation within the endoplasmic reticulum. These propeptides are then cleaved from the collagen triple helix molecule during its secretion, after which the collagens polymerize into extracellular collagen fibrils. Thus, the amount of free propeptides directly correlates with collagen molecule synthesis. Procollagen Type I C-peptide (PIP) has also been extensively referenced in correlation studies between collagen levels and certain health disorders such as bone disease, alcoholic liver disease, liver cirrhosis and scirrhous (Borrmann type IV) adenocarcinoma of the stomach.
The Procollagen Type I C-Peptide (PIP) EIA Kit (Precoated) is a 96 well format in vitro enzyme immunoassay intended for the quantification of human, bovine, canine and horse PIP in plasma, serum, cell culture extract, cell culture supernatant and other biological fluids. It is a solid phase procollagen ELISA based on a sandwich design that utilizes two mouse monoclonal PIP antibodies, one of which is coated onto the plate, the other of which is peroxidase-labeled, for the detection of PIP. The procollagen ELISA takes advantages of a one-step format wherein test samples and peroxidase-labeled anti-PIP are simultaneously added to the wells of the plate and incubated. During incubation, PIP becomes bound to the antibody coating the plate and is tagged by peroxidase-labeled anti-PIP at its opposite side. A substrate (H2O2, TMBZ) is added and the reaction between the peroxidase and substrate results in color development. The amount of sample PIP is determined by measuring absorbance using an EIA plate reader. Accurate PIP sample concentrations can be determined by comparing their specific absorbances with that obtained for the supplied kit standard (via a plotted standard curve).