Vitamin D binding Protein (VDBP) ELISA

Vitamin D binding protein (VDBP, also known as group-specific component / Gc protein)
is a multifunctional serum protein which is formed in the liver. High estrogen
levels, caused e.g. by pregnancy or hormonal birth control, stimulate its synthesis.
VDBP can be found in plasma, ascites, liquor, urine and at the surface of various cell
types.
In the blood, VDBP binds the bigger part of the circulating 25-OH vitamin D and
brings it to the kidneys, where it is transformed into the hormone 1,25-(OH)2 vitamin
D.
In addition, VDBP binds monomeric actin at the ratio of 1:1. Actin is an intracellular
protein which is available as monomer or filament. Massive tissue destruction or
cell death cause the plasma level of actin to rise significantly, whereupon VDBP-actin
complexes are formed which are removed quickly. Hence the VDBP level of trauma
or sepsis patients decreases quickly, especially in patients with a high level of multiorgan
failure.
Furthermore VDBP is a precursor of the immunomodulating protein Gc-MAF (Gc
protein-derived macrophage activating factor) which increases the activity of macrophages
against tumours.