Osteocalcin is a 49 amino acid peptide found exclusively in bone tissue which is highly conserved among species. It is a vitamin K- and D-dependent protein produced by osteoblasts, osteocytes and odontoblasts. It is deposited in the extracellular bone matrix and is found in the serum.
Serum osteocalcin, hydrolyzed in the kidney and liver, is considered as a specific marker of osteoblast activity and bone formation rate. It may be involved in regulation of osteoblast function, regulation of bone turnover and/or mineralization.
Des-gamma-carboxylated osteocalcin serves as a substrate for vitamin K-dependent carboxylase, which modifies Glu17, Glu21, and Glu24 to Gla residues.