Biochemistry - Amino Acid Metabolism - Discussion

Why is Phenylpyruvate the most toxic amongst these. I believe it is Phenylalanine. This is because a build up of Phenylalanine in the body leads to a diseased condition known as phenylketonuria which is an inborn error of metabolism.

What will happen if phenylpyruvate concentration in the body exceeds certain limits?

A person with PKU will subject to cause conversion of phenylalanine to phenylpyruvate that is with phenylpyruvate is toxic and not phenylalanine.

Why is the answer is B? I think it should be phenylalanine.

PKU as we know is due to lack of enzyme phenylalanine hydroxylase and so phe cannot be converted to tyr, rahter it forms phenylpyruvic acid which is found in urine of patients with PKU disorder.

Phenylpyruvate is formed when phenylalanine loose its amino group. Accumulation of phenylalanine will increase the levels of phenylpyruvate and deprives the brain of alph ketoglutarate which will cause the brain to shut the TCA cycle and hence aerobic respiration. This condition is known as phenylketonuria victims start to have mental issues.

It can again inhibit the expression of tyrosinase enzyme leading to deficiency of pigmentation.