Biochem q

[shigella123]

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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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Does rate limiting enzyme always increase in ischemic conditions? I chose, C. PD thinking it would switch and start producing lactic acid in ischemic condition. Does that not happen?


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complete ans:
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, glycolysis become 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.

 

[Matteo]

Pyruvate --> Lactate is catalyzed by Lactate DH, not Pyruvate Dehydrogenase (Pyruvate --> Acetyl CoA)

 

[shigella123]

Oh, I see why it's not PD after looking at the pathways. I needed to review that. Thanks