10-06-2006, 08:06 AM
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?
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
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?
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