A heptapeptide was found to have an amino acid composition of asp. leu, lys, 2 met, phe and tyr. a) Trypsin has no effect on the heptapeptide. b) One cycle of Edman degradation renders: N H C-CH2 N H S c) Chymotrypsin treatment yields a dipeptide and a tetrapeptide, as well as a free amino acid. d) The tetrapeptide generated by chymotrypsin is known to contain leu, lys, and met. No met is present in the dipeptide. e) Cyanogen bromide treatment generates a dipeptide, a tetrapeptide, and free lys.