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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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submitted by haliburton(83),

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 +  




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submitted by humble_station(7),

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.





 +0  upvote downvote
submitted by humble_station(7),

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.