Carboxylation and decarboxylation dynamics of osteocalcin (IMAGE)
Caption
Carboxylation and decarboxylation dynamics of osteocalcin
Glu-OCN is secreted by osteoblasts and then undergoes γ-carboxylation at glutamic acid residues at positions 17, 21, and 24, a reaction catalyzed by γ-glutamyl carboxylase (GGCX) in a vitamin K-dependent manner. The fully carboxylated form, Gla-OCN, is incorporated into the extracellular matrix (ECM) of bone tissue. During bone resorption, the acidic microenvironment facilitates the decarboxylation of Gla-OCN, converting it back to Glu-OCN, which is subsequently released into the systemic circulation. Glu-OCN: undercarboxylated osteocalcin; GGCX: γ-glutamyl carboxylase; Gla-OCN: noncarboxylated, carboxylated; ECM: extracellular matrix.
Credit
Ying-ying Ding, Yu-ying Yang, Li-hao Sun, Jian-min Liu, Bei Tao.
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