The encephalin are naturally occurring compounds found in the central nervous sy

Question

The encephalin are naturally occurring compounds found in the central nervous system whose activity is imitated by morphine. The amino acid composition of one of the encephalin is 2Gly, Met. Phe, Tyr. Reaction of this pentapeptide with 8-dimethylaminonapthalensulfonylchloride (damsel chloride) and subsequent acid catalyzed hydrolysis affords the damsel derivative of tyrosine as the only modified amino acid. When the encephalin is treated with cyanogen's bromide, no cleavage occurs. Partial hydrolysis of the pentapeptide with Chymotrypsin gives only tyrosine, methionine and a tripeptide. What is the sequence of the encephalin? What does the damsel derivative of the tyrosine look like?

Explanation / Answer

a). Chymotrypsin cleaves at the c-terminal end of aryl amino acids (phenyl alanine, tyrosine and tryptophan). Thus, the number of fragments produced are 2. The pentapeptide sequence is, Gly-Gly-Phe-Tyr-Met. Cleavage at the C-terminal of the tyrosine releases methionine, cleavage at the C-terminal of the Phe releasea Tyr.

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