ques

Prep for USMLE Forum

» Log in | Register

Forum

Step 1

Match

Prep4USMLE Forum » USMLE Step 1 Forum » Biochemistry Forum

ques

Author

11 Posts

drpkaur
Forum Guru
avatar

Topics: 195
Posts: 808

09/11/06 - 10:46 AM

Chymotrypsin is one of the major digestive enzymes secreted by the pancreas and is also used in the determination of the primary structure of proteins. Given a polypeptide with the following sequence

Asp-Glu-Pro-Met-Lys-Phe-Gly-Gly-Glu-Tyr-Arg-Phe-Glu-Pro

Which of the following peptides could result from chymotryptic cleavage?

A. Asp-Glu-Pro-Met

B. Phe-Glu-Pro

C. Gly-Gly-Glu-Tyr-Arg-Phe

D. Asp-Glu-Pro-Met-Lys-Phe

E. Lys-Phe-Gly-Gly-Glu-Tyr

Leopard
Forum Guru
avatar

Topics: 30
Posts: 401

09/11/06 - 11:09 AM

I think the answer is C & D

Best of luck

___________________
FA is just a good revision book.It is not a "real" learning tool.

drpkaur
Forum Guru
avatar

Topics: 195
Posts: 808

09/11/06 - 12:03 PM

can u explain why??

Leopard
Forum Guru
avatar

Topics: 30
Posts: 401

09/11/06 - 12:28 PM

Trpsinogen cleaves that peptide bond in which Carboxyl contribution is from

Aromatic aminoacids
Leucine

GL

___________________
FA is just a good revision book.It is not a "real" learning tool.

docarchana
Forum Guru

Topics: 70
Posts: 515

09/11/06 - 02:55 PM

r both C & D correct drpkaur..

drpkaur
Forum Guru
avatar

Topics: 195
Posts: 808

09/11/06 - 05:24 PM

http://www.bio.mtu.edu/campbell/cleavage.htm
correct answer is d..

Leopard
Forum Guru
avatar

Topics: 30
Posts: 401

09/11/06 - 05:38 PM

drpkaur [url="http://www.bio.mtu.edu/campbell/cleavage.htm" target=_blank wrote:
http://www.bio.mtu.edu/campbell/cleavage.htm[/url]
correct answer is d..

Bond will also be broken on the carboxyl terminal of 2nd phenylalanine.What does stop it from breaking??? Would please explain it ?? thanks

___________________
FA is just a good revision book.It is not a "real" learning tool.

blueocean
Forum Senior
avatar

Topics: 15
Posts: 195

09/12/06 - 06:09 AM

Leopard the bound can be broken where you said but you don't have this choice in the answers!

docsrinu
Forum Elite

Topics: 26
Posts: 213

09/12/06 - 08:28 AM

blue ocean, C corresponds to that ans..

Leopard
Forum Guru
avatar

Topics: 30
Posts: 401

09/12/06 - 10:24 AM

#10

blueocean wrote:
Leopard the bound can be broken where you said but you don't have this choice in the answers!

Please look at the chain

Asp-Glu-Pro-Met-Lys-Phe- (1st place ) Gly-Gly-Glu-Tyr-Arg-Phe (2nd place)-Glu-Pro

Asp-Glu-Pro-Met-Lys-Phe =choice D

Gly-Gly-Glu-Tyr-Arg-Phe = choice C

Glu-Pro= not in the choice

Best of luck

___________________
FA is just a good revision book.It is not a "real" learning tool.

blueocean
Forum Senior
avatar

Topics: 15
Posts: 195

09/12/06 - 11:31 AM

#11

Sorry!

I readed second gly like glu!
You guys are right!

You don't have permission to post.