What is the Origin of Post-Translational Carboxylation?

The term is derived from its sequential position in protein synthesis: post-translational indicates that the event occurs after the primary protein chain (translation) is complete, and carboxylation specifies the chemical addition of the carboxyl group. Its discovery is intrinsically linked to the elucidation of the blood clotting cascade and the identification of vitamin K's indispensable role as a cofactor for the carboxylase enzyme. This understanding clarified a vital link between nutrient status and protein function.

What is the Mechanism of Post-Translational Carboxylation?

The mechanism is catalyzed by the enzyme gamma-glutamyl carboxylase, which requires reduced vitamin K (hydroquinone) as an essential cofactor. The enzyme converts specific glutamic acid residues within the target protein into gamma-carboxyglutamic acid (Gla). These newly formed Gla residues are chemically necessary to chelate calcium ions, which is the functional switch that allows these proteins to bind to phospholipid surfaces and initiate their biological action, such as forming a fibrin clot or mediating bone mineralization.

Post-Translational Carboxylation ∞ Area

Post-Translational Carboxylation

Meaning

Post-Translational Carboxylation is a crucial biochemical modification process that occurs after a protein has been synthesized by the ribosome, specifically involving the enzymatic addition of a carboxyl group (COO⁻) to a glutamic acid residue. This modification is essential for the biological activity of several key proteins, most notably the vitamin K-dependent coagulation factors and certain bone-regulating proteins like osteocalcin. The integrity of this process is paramount for maintaining hemostasis and skeletal health.