5 of 15 Sapling Learning N-Tosylamido-L irreversibly inhibits chymotrypsin, and

Question

5 of 15 Sapling Learning N-Tosylamido-L irreversibly inhibits chymotrypsin, and is used as to label the active site histidine residue. The COCH2CI group is the reactive group that binds to the His residue. yl, also called tosyl phenylalanyl chloromethyl ketone, (TPCK) (a) Why does chymotrypsin bind TPCK? O interactions with the active site of chymotrypsin, reversibly outcompeting the usual substrate. O The serine residue at position 195 in chymotrypsin is a strong nucleophile residue The phenyl group of TK is structurally similar to regular chymotrypsin o The chlorine of TPCK is a strong nucleophile, and atacks the His 157 TPCK substrates (b) Trypsin, another serine protease, does not bind TPCK. How could TPCK be modified to enable its recognition by trypsin? Choose the most likely substrate, below. Scroll down to see the complete structures. O c 4, 0

Explanation / Answer

Binding of TPCK

(a) TPCK binds to chymotrypsin as,

TPCK is a polar molecule and esaily forms several noncovalent interactions with the active site of chymotrpsin reversibly outcompeting the usual substrate.

(b) Serine is a polar molecule. To make TPCK similar so it binds easily to trypsin in identification, the substrate would look like,

B

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