1559T_ch26_454-46810/20/0515:39Pa9e463 ⊕ EQA Solutions to Problems.463 The final fragp 46.Products of degradation,in order of appearance CH-CHSCH The last product to appear from leu-enkephalin is CH-CH(CH 47.Look first for a piece that ends with an amino acid that should not be a site of cleavage by one of the chymotrypsin fragments end in Pne end of the intact hormone.Now itsa matter of matching up all the pieces.Start with this end picce from trypsin hydrolysis and overlap it with chymotrypsin fragments. (Trypsin piece) Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe (Chymotrypsin pieces) Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro Leu-Glu-Phe Ser-Tyr-Ser-Met-Glu-His-Phe-ArgTrp-Gly-Lys Pro-Val-Gly-Lys Pro-Val-Lys Val-Tyr Ser-Tyr Ser-Met-Glu-His-Phe Arg-Trp Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr .d the o h SerTy-SeMet Hi he Arg Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-GIn-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe 48.Start at the carboxy-terminal end. 00 1.Phe +(CH3)COCOCOC(CH3)3-Boc-Phe (N-protected Phe) The final fragment, Phe-Arg, clearly is at the end, overlapping the Phe in position 8. So the answer is Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg. 46. Products of degradation, in order of appearance The last product to appear from leu-enkephalin is 47. Look first for a piece that ends with an amino acid that should not be a site of cleavage by one of the enzymes. All the chymotrypsin fragments end in Phe, Trp, or Tyr, so that’s no help. The trypsin results are more useful. It only cleaves after Arg or Lys, so the 18-amino acid fragment ending in Phe must be at the end of the intact hormone. Now it’s a matter of matching up all the pieces. Start with this end piece from trypsin hydrolysis and overlap it with chymotrypsin fragments. (Trypsin piece) Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe (Chymotrypsin pieces) Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro Leu-Glu-Phe Now identify a chymotrypsin piece to overlap with the Val-Tyr- front end of the trypsin piece and then continue the process, all the way to the N-terminal end (the “beginning”) of the entire hormone. Ser-Tyr-Ser-Met-Glu-His-Phe-Arg Trp-Gly-Lys Pro-Val-Gly-Lys Pro-Val-Lys Val-Tyr￾Ser-Tyr Ser-Met-Glu-His-Phe Arg-Trp Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr The complete answer is read directly, starting at Ser-Tyr- (just above), overlapping Val-Tyr with the large trypsin piece, and then on to the end: Ser-Tyr-Ser-Met-Gln-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-Gly-Lys-Lys￾Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe 48. Start at the carboxy-terminal end. 1. Phe (CH3)3COCOCOC(CH3)3 O O Boc-Phe (N-protected Phe) S O N NH CH2CH(CH3)2 S O N NH CH2 S O N NH CH2CH2SCH3 S O N OH NH S O 2 N NH CH2 Solutions to Problems • 463 1559T_ch26_454-468 10/20/05 15:39 Page 463