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Old 08-09-2012
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Biochemistry Myocardium and Cocaine

At autopsy of 28-year-old man, the left ventricle of the heart shows classic contraction band necrosis of the myocardium. Cocaine and its metabolites are detected in body fluids. Activity of which of the following enzymes was most likely increased in the patient's myocardial cells prior to his death?

A. phosphoenolpyruvate carboxykinase
B. PFK-1
C. Pyruvate dehydrogenase
D. Succinate dehydrogenase
E. Transketolase
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Old 08-09-2012
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Default my answer

D. Succinate dehydrogenase
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Old 08-09-2012
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answer is PFK -1
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Old 08-09-2012
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PFK-1 since its a part of glycolysis.
Every reaction after glycolysis will stop, ruling out C and D. The cardiac muscle has no business doing gluconeugenesis or participating in HMP shunt, so A and E are incorrect too.
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Old 08-09-2012
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Originally Posted by smanthrav View Post
PFK-1 since its a part of glycolysis.
Every reaction after glycolysis will stop, ruling out C and D. The cardiac muscle has no business doing gluconeugenesis or participating in HMP shunt, so A and E are incorrect too.
but I was thinking that D) Succinate dehydrogenase is a part of ETC -cocaine would promote glycolysis indeed -> more NADH, FADH synthesis -> more ATPs (inhibit PFK 1) + increasing O2 demand -> insufficient O2 supply -> infarction

Also I think PFK 1 is inhibited by low pH, so I think its level was low right before myocardium infarction.
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Old 08-09-2012
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hmmm... I thought it over and you guys are right - PFK 1 will be increased. I overanalyzed this question
myocardial infarction-low ATP/high AMP-> high PFK 1
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Old 08-10-2012
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Default sorry for late reply guys

Answer is B- PFK-1 or Phosphofructokinase-1
Cocaine blocks the reuptake of NE resulting in trachycardia as well as excessive vasoconstriction of coronary vessels, leading to ischemia and infarction of heart tissue known as contraction band necrosis. Under these pathological conditions, myocardial cells switch to anaerobic metabolism and therefore, glycolysisbecome the sole source of ATP via substrate-level phosphorylation by phosphoglycerate kinase and pyruvate kinase. PFK-1 is the rate- limiting enzyme of glycolysis, and its activity would therefore be increased.
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