sarika
Forum Guru
Topics: 195
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During the isolation of Met-enkephalin (Tyr-Gly-Gly-Phe-Met) from post-mortem human brain tissue, researchers find
that the peptide is rapidly degraded by peptidases in 1 minute at 37 C. Detailed analysis of the peptide cleavage
pattern of Met-enkephalin is investigated with two candidate enzymes. Using the drug bestatin, the investigators
found no detectable Tyr-Gly-Gly-Phe-Met but did find significant concentrations of Tyr-Gly-Gly. Using thiorphan,
there was no detectable Tyr-Gly-Gly-Phe-Met, but there was a high concentration of Tyr. Which of the following is the
best conclusion about Met-enkephalin metabolism that can be drawn from these data?
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A. Bestatin inhibits an aminopeptidase, and thiorphan inhibits an endopeptidase in the
degradative pathway
B. Bestatin inhibits a carboxypeptidase in the degradative pathway
C. Bestatin inhibits an endopeptidase in the degradative pathway
D. Thiorphan inhibits an aminopeptidase, and bestatin inhibits an endopeptidase in the degradative pathway
E. Thiorphan inhibits an aminopeptidase in the degradative pathway
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| robin082006
Forum Hero
Topics: 471
Posts: 5,125
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let's me try
I saw this q somewhere
aminopeptidase: cuts amino acid at the end of amino acid chain
endopeptidase: cuts inner bonds of amino acid chain
when using bestatin, Tyr-Gly-Gly remained. This means that the bond between Gly and Phe has ben cut--> endopeptidase acted on this bond. Therefore we infer that bestatin cannot be endopeptidase inhibitor, the only choice is aminopeptidase inhibitor.
when using thiorphan, there was Try. This means that the bond between Try and Gly has been cut, this is the bond at the end of amino acid chain--->aminopeptidase acted on this bond---> thiorphan cannot be aminopeptidase inhibitor--->it is endopeptidase inhibitor
so ans is A
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| skyhigh
Forum Guru
Topics: 105
Posts: 561
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agree
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| nadiabarati
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How about the probability of carboxypeptidase activity?
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