Anniversary Issue Contribution Correspondence to:

Vitamin K,discovered in the 1930s, functions as cofactor for the posttranslational carboxylation of glutamate residues. Gamma-carboxy glutamic acid (Gla)-residues were first identified in pro-thrombin and coagulation factors in the 1970s; subsequently, extra-hepatic Gla proteins were described,including osteocalcin and matrix Gla protein (MGP). Impairment of the function of os-teocalcin and MGP due to incomplete carboxylation results in an increased risk for developing osteoporosis and vascular cal-cification, respectively, and is an unexpected side effect of treat-ment with oral anticoagulants. It is conceivable that other side effects, possible involving growth-arrest-specific gene 6 (Gas6