Question

A tripeptide $x$ on partial hydrolysis gave two dipeptides Cys-Gly and Glu-Cys.
Identify the tripeptide,

$\stackrel{+}{N}{H}_3-\stackrel{C{H}_{2}C{H}_{2}COOH}{\stackrel{|}{CH}}-\underset{Glu-Cys}{\underset{O}{\underset{||}{C}}}-NH-\stackrel{C{H}_{2}SH}{\stackrel{|}{CH}}-\underset{O}{\underset{||}{C}}-\stackrel{-}{O}$

and

$\stackrel{+}{N}{H}_3-\stackrel{C{H}_{2}SH}{\stackrel{|}{CH}}-\underset{Cys-Gly}{\underset{O}{\underset{||}{C}}}-NH-C{H}_2-\underset{O}{\underset{||}{C}}-\stackrel{-}{O}$

• A. Glu-Cys-Gly
• B. Gly-Glu-Cys
• C. Cys-Gly-Glu
• D. Cys-Glu-Gly

Answer 1

The correct option is A Glu-Cys-Gly

$\stackrel{+}{N}{H}_3-\stackrel{C{H}_{2}C{H}_{2}COOH}{\stackrel{|}{CH}}-\underset{Glu-Cys}{\underset{O}{\underset{||}{C}}}-NH-\stackrel{C{H}_{2}SH}{\stackrel{|}{CH}}-\underset{O}{\underset{||}{C}}-\stackrel{-}{O}$

and

$\stackrel{+}{N}{H}_3-\stackrel{C{H}_{2}SH}{\stackrel{|}{CH}}-\underset{Cys-Gly}{\underset{O}{\underset{||}{C}}}-NH-C{H}_2-\underset{O}{\underset{||}{C}}-\stackrel{-}{O}$

The tripeptide is Glu - Cys - Gly