Mediates the vitamin K-dependent carboxylation of glutamate residues to calcium-binding gamma-carboxyglutamate (Gla) residues with the concomitant conversion of the reduced hydroquinone form of vitamin K to vitamin K epoxide. 2,3-epoxyphylloquinone + 4-carboxy-L-glutamyl-[protein] + H(+) + H2O = CO2 + L-glutamyl-[protein] + O2 + phylloquinol Optimum pH is 7. Monomer. May interact with CALU (By similarity). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The vitamin K-dependent protein substrates of carboxylase have usually a propeptide that binds to a high-affinity site on the carboxylase. CO(2), O(2) and reduced vitamin K are cosubstrates. Belongs to the vitamin K-dependent gamma-carboxylase family.