Question

1. Name the principal catabolites of the carbon skeletons of the protein amino acids and the major metabolic fates of these catabolites.

2. Outline the metabolic pathways for tyrosine, phenylalanine, methionine, cysteine and branched chain amino acids, and identify reactions associated with clinically significant metabolic disorders.

3. Explain why metabolic defects in different enzymes of the catabolism of a specific amino acids tyrosine, phenylalanine, methionine, cysteine and branched chain amino acids) can be associated with similar clinical signs and symptoms.

4. Draw analogies between the reactions that participate in the catabolism of fatty acids and of the branched-chain amino acids

Answer 1

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The first question is being answered below:

The Principal catabolites of the carbon amino acids are:

pyruvate,

acetyl CoA,

acetoacetyl CoA,

α-ketoglutarate,

succinyl CoA,

fumarate,

oxaloacetate

The fates of the carbon skeletons of amino acids after the removal of the α-amino group.

The strategy of amino acid degradation is to transform the carbon skeletons into major metabolic intermediates that can be converted into glucose or oxidized by the citric acid cycle.

Amino acids that are degraded to acetyl CoA or acetoacetyl CoA are termed ketogenic amino acids because they can give rise to ketone bodies or fatty acids. Amino acids that are degraded to pyruvate, α-ketoglutarate, succinyl CoA, fumarate, or oxaloacetate are termed glucogenicamino acids. The net synthesis of glucose from these amino acids is feasible because these citric acid cycle intermediates and pyruvate can be converted into phosphoenolpyruvate and then into glucose.