question_answer

A tripeptide (X) on hydrolysis gives three amino acids:

\[(N{{H}_{2}}-\underset{R}{\mathop{\underset{|}{\mathop{C}}\,}}\,H-COOH)\]

\[(N{{H}_{2}}-\underset{R'}{\mathop{\underset{|}{\mathop{C}}\,}}\,H-COOH)\]

\[N{{H}_{2}}-\underset{R''}{\mathop{\underset{|}{\mathop{C}}\,}}\,H-COOH)\]

(X) on reaction with \[N{{H}_{2}}N{{H}_{2}}\] gives a dipeptide (Y) and amino acid .

The dipeptide (Y) is hydrolysed by carboxypeptides enzyme and gives amino acid. What is the structure of?

A) \[C-A-B\]    

B)                    \[B-A-C\]           

C)   \[A-B-C\]          

D)        \[B-A-C\]

Correct Answer: A

Solution :

[a] (A is also C-terminal amino acid) From the above reaction, it is clear that the amino acid [c] is N-terminal. Hence the sequence is \[(C\to A\to B)\]. \[C-A-B\]