Aminotransferase must deaminate one amino acid and add an amino group to another

Question

Aminotransferase must deaminate one amino acid and add an amino group to another amino acid. How do the two processes differ?

Choose one of the following:

A. The second part of the reaction takes place at a separate amino acid residue in the active site.

B. The first reaction involves the formation of a Schiff base, but the second does not

C. The second part of the reaction (adding the amino group) is the reverse of the first (deamination).

D. The coenzyme PLP must be activated by an external amino group before it can catalyze the removal of the amino group from the first amino acid.

Explanation / Answer

C. The second part of the reaction (adding the amino group) is the reverse of teh first (deamination).

The first amino acid forms a schiff's base with the enzyme pyridoxal phosphate, with transfer of amino group to the enzyme, and the 2-keto acid of the first amino acid is released. The enzyme is now pyridoxamine phosphate.

The same enzyme with amino group (pyridoxamine phosphate) forms a schiff's base with the second keto acid, to which the amino group is transferred. This reaction is exactly the opposite of the first reaction

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