OBJECTIVE Newborns routinely receive vitamin K to prevent vitamin K deficiency bleeding. The efficacy of oral vitamin K administration may be compromised in infants with unrecognized cholestasis. We aimed to compare the risk of vitamin K deficiency bleeding under different prophylactic regimens in infants with biliary atresia. PATIENTS AND METHODS From Dutch and Danish national biliary atresi...

The vitamin K metabolism of three patients with factitious purpura due to brodifacoum ingestion was studied. These patients, who presented with bleeding disorders due to deficiency of the vitamin K-dependent blood clotting proteins, were refractory to vitamin K1 at standard doses and required fresh frozen plasma to control bleeding until large doses of vitamin K1 were used. Metabolic studies de...

Vitamin K epoxide can occur as a pair of optical isomers due to the asymmetry of the oxirane ring substituents. The stereoselectivity of vitamin K-epoxide reductase for the oxirane ring configuration was determined by recovery of the partially resolved unreacted substrate following incubations of racemic vitamin K epoxide with rat liver microsomes. The substrate ws enriched for the (--)-enantio...

Vitamin K has long been associated solely with its role in haemostasis. The last two decades brought new intriguing insights to the function of vitamin K. While the present recommendations for daily intake are based mainly on amounts required to maintain coagulation, they may not be high enough to ensure adequate functions of vitamin K not involved in blood clotting, In the present review the r...

Vitamin K hydroquinone is oxidised to the epoxide form (K>O) during vitamin K-dependent posttranslational gamma-glutamyl carboxylation resulting in biological active so called vitamin K-dependent proteins. In turn, K>O is reduced by the enzyme VKORC1 (vitamin K epoxide reductase complex component 1) to complete the vitamin K cycle. To investigate the biological role of VKORC1 in vivo, we genera...