[sam01]

A newborn presents with severe acidosis, vomiting, hypotonia, and neurologic deficits. Serum analysis reveals elevated levels of lactate and alanine. These observations suggest a deficiency in which of the following enzymes?

A. Alanine aminotransferase
B. Glutamate dehydrogenase
C. Lactate dehydrogenase
D. Pyruvate carboxylase
E. Pyruvate dehydrogenase

 

[aungawa]

i think D. Pyruvate carboxylase

 

[khanar]

Why?

i think D. Pyruvate carboxylase

Yeah, but you have to explain why?

 

[sam01]

E -pyruvate deshydrogenase is the correct answer

E is correct.Pyruvate dehydrogenase catalyzes the irreversible conversion of pyruvate to acetyl-CoA. If it's absent, pyruvate will be used in other pathways instead. Pyruvate
will be converted to alanine via alanine aminotransferase and to lactate via lactate
dehydrogenase .
pyruvate will be increased with concomitant increase in lactic acid and alanine via transamination and severe reduction in ATP production.Then u have lactic acidosis , neurologic defects...

 

[theartofbone]

E is correct.Pyruvate dehydrogenase catalyzes the irreversible conversion of pyruvate to acetyl-CoA. If it's absent, pyruvate will be used in other pathways instead. Pyruvate
will be converted to alanine via alanine aminotransferase and to lactate via lactate
dehydrogenase .
pyruvate will be increased with concomitant increase in lactic acid and alanine via transamination and severe reduction in ATP production.Then u have lactic acidosis , neurologic defects...

I whole heartedly agree

 

[doctorF]

at the end of glycolysis forms pyruvate...

this pyruvate have three ways it can go

1) form acetyl co A using pyruvate dehydrogenase as enzyme and NAD,FAD, thiamine pyrophosphate and coA as cofactors
which it does in normal circumstances and continues TCA cycle

2) forms Lactate using Lactate dehydrogenase and NAD as cofactor... it does that in PDH or any of the pdh cofactor deficience or anaerobic conditions

3) forms alanine also in PDH or any of the pdh cofactor deficiency

so lactate elevation and alanine elevation is a clearcut sign of PDH deficiency

 

[ecgram]

totally agree with doctorF

 

[deanshao]

Why wouldn't pyruvate carboxylase produce the same result? A deficiency in pyruvate carboxylase would lower the production of OAA, there will be a similar decrease in the production of citrate, resulting in pyruvate going through other shunts that would produce lactate and alanine.