Question

13. Describe the type of reaction and the coenzyme required for the first step in amino acid catabolism?

Answer 1

Q.13. Answer-

1. Amino acids are catabolism occurs in liver where transaminases transfers alpha amino group of amino acid to the alpha keto acids and this reaction is known as transamination reaction.

2. In transamination reaction alpha amino group of amino acid is removed and transferred to the alpha keto acid and leaving alpha keto acid analog to amino acid so that there is no net loss of amino group.

3. Generally alpha ketoglutarate acts as amino group acceptor and converted into glutamate and this glutamate acts as amino group donor in various biosynthetic reactions or carries amino group towards production of nitrogenous waste products.

4. Depending on amino acid enzyme is named like Alanine aminotransferase, aspartate aminotransferase etc. and all aminotransferase has pyridoxal phosphate (PLP) as coenzyme that is tightly bound to enzyme. PLP acts as intermediate carrier of amino groups at the active site of enzyme as in pyridoxal phosphate (aldehyde form) accepts amino group and pyridoxamine phosphate (aminated form) donate its amino group to alpha keto acid.

5. During the reaction amino acid binds to the active site of enzyme and donates its amino group to the pyridoxal phosphate and keto acid analog of amino acid leaves the enzyme. Then incoming keto acid which is acceptor of amino group binds to the active site of enzyme and accepts amino group from pyridoxamine phosphate and leaves in the form of amino acid.