Q.34 The reactions leading to the formation of amino acids from the TCA cycle intermediates are
(A) carboxylation (B) isomerization (C) transamination (D) decarboxylation
TCA Cycle to Amino Acids: Transamination Key Reaction Explained
TCA cycle intermediates like α-ketoglutarate and oxaloacetate directly convert to amino acids through specific biochemical reactions. The correct answer to the multiple-choice question is (C) transamination. This process enables non-essential amino acid biosynthesis in cells.
Correct Answer: Transamination
Transamination transfers the amino group from an amino acid donor, typically glutamate, to a keto acid derived from TCA cycle intermediates, forming new amino acids. For instance, α-ketoglutarate (from TCA) accepts an amino group to become glutamate, while oxaloacetate forms aspartate. Enzymes called aminotransferases, requiring pyridoxal phosphate (vitamin B6), catalyze these reversible reactions central to nitrogen metabolism.
Option Breakdown
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(A) Carboxylation: Adds CO₂ to substrates, as in pyruvate to oxaloacetate, but does not introduce amino groups for amino acid formation from TCA intermediates.
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(B) Isomerization: Converts molecules like glucose-6-phosphate to fructose-6-phosphate, rearranging atoms without adding nitrogen, irrelevant to amino acid synthesis here.
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(C) Transamination: Correct, as it directly links TCA keto acids to amino acids via aminotransferase enzymes.
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(D) Decarboxylation: Removes CO₂, producing amines from amino acids (e.g., glutamate to γ-aminobutyric acid), but opposite of formation from TCA intermediates.
Biochemical Relevance
These reactions replenish non-essential amino acids during protein synthesis and maintain TCA cycle anaplerosis. In biotechnology, understanding transamination aids microbial fermentation optimization for amino acid production.
