A young woman presented with a 2 yr history of a severe bleeding disorder and marked deficiencies in all 4 vitamin-k-dependent factors. Metabolic studies with tracer doses of 3H-vitamin k1 suggested that the patient m...
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A young woman presented with a 2 yr history of a severe bleeding disorder and marked deficiencies in all 4 vitamin-k-dependent factors. Metabolic studies with tracer doses of 3H-vitamin k1 suggested that the patient might be taking an oral anticoagulant;subsequently her plasma was found to contain a substance identical to phenindione in its spectrophotometric and chromatographic properties. The half-disappearance times of factors II, IX and X were measured after the administration of concentrate of these factors and were found to conform with published figures. The concentrate controlled the patient''s excessive bruising and prolonged skin and gingival bleeding. Factor VII may not be essential in reversal of the bleeding disorder induced by anticoagulant overdose.
We wished to investigate the mechanism of decreased serum vitamin k1 after bone fractures. Vitamin k1 plays a role in bone formation because it is required as a cofactor for the transformation of glutamic acid (Glu) r...
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We wished to investigate the mechanism of decreased serum vitamin k1 after bone fractures. Vitamin k1 plays a role in bone formation because it is required as a cofactor for the transformation of glutamic acid (Glu) residues on proteins to γ-carboxyglutamic acid (Gla) residues. The double carboxy group on Gla residues has high affinity for the binding of calcium. Bone formation involves vitamin k-dependent small peptide osteocalcin (bone-Gla-protein) that is secreted by osteoblasts. Serum concentrations of vitamin k1 reflect in part the capacity of the serum to carry the vitamin. Vitamin k1 is a lipid, and little is known about the binding of this vitamin to proteins other than that it is transported in serum by the lipoproteins. It is not known whether there is a specific "vitamin k1-binding protein" in tissues as has been suggested for vitamin E as a "tocopherol-binding protein" (1).
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