You have a purified a new neurotransmitter. Further analysis shows this neurotransmitter is an octapeptide composed of one Arg, one Gly, one Glu, two...

You have a purified a new neurotransmitter. Further analysis shows this neurotransmitter is an octapeptide composed of one Arg, one Gly, one Glu, two Met, one Ser, one Trp, and one Tyr.

Treatment with cyanogen bromide, which cleaves carboxy-terminal to Met, produced 3 peptides: a tripeptide composed of Glu, Ser, and Trp; a tripeptide composed of Arg, Gly, and Met, and a dipeptide composed of Met and Tyr.

Treatment with Trypsin, which cleaves carboy-terminal to Arg and Lys, produced 2 peptides: a tripeptide composed of Arg, Met, and Tyr, and a pentapeptide composed of Glu, Gly, Met, Ser, and Trp.

The amino-terminal amino acid in this neuropeptide is:

a. Trp

b. Gly

c. Arg

d. Met

e. Tyr

Another user asked this question and someone answered that the answer is e. Our question is WHY? 

Mm}, Am [1}. '0an): Glrtll. [la [13‘ L15 (1],Metal], PM [1). Serll). Thrfl], 1113(1). Tyrtl) Aso-Thr-T rp-Met-lle-LysAfter treatment with in sin n obtain the [ollowln l'ra ments:...