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NBME 22 Answers

nbme22/Block 3/Question#12

An 82-year-old woman has been bedridden since ...

Carboxylation of precursor proteins

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warfarin inhibits the synthesis of factors II, VII, IX, X, C, and S by blocking reduction of oxidized vitamin K. The enzyme Epoxide Reductase is inhibited by warfarin. The reduced (active) form of vit. K is a cofactor for gamma-glutamyl carboxylase.

link981  So factors II, VII, IX, and X are precursor proteins? GTFO +  




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submitted by sup(3),

Why not PGI2 by way of ASA? Especially given other answer choices of proteins C + S: doesn't warfarin also suppress these?

imnotarobotbut  Protein C and S are ANTI-thrombotic, so although Warfarin does decrease them, they wouldn't decrease the patient's risk for thrombosis +  
epr94  the question ask "suppression" of which one will decrease risk of thrombosis if you suppress C and S which and anti-thrombotic you get thrombotic +  




Warfarin inhibits Vit K dependent synthesis of factors & proteins.

Vit K is necessary for the maturation of clotting factors II, VII, IX, X and protein C & S

So a drug that can inhibit the carboxylation of precursor proteins or in other words inhibit the maturation of the clotting factors will decrease the risk of thrombosis in this patient.





Warfarin inhibits Vit K dependent synthesis of factors & proteins.

Vit K is necessary for the maturation of clotting factors II, VII, IX, X and protein C & S

So a drug that can inhibit the carboxylation of precursor proteins or in other words inhibit the maturation of the clotting factors will decrease the risk of thrombosis in this patient.