a) Sketch a graph of 1/v o vs. 1/[S] for the 4 different compounds (labeling eac
ID: 850805 • Letter: A
Question
a) Sketch a graph of 1/vo vs. 1/[S] for the 4 different compounds (labeling each line 1-4). Label the relevant points on your sketch that are expected given the information provided about the compounds.
b) Compare the compounds 2,3, and 4 with the normal substrate and draw conclusions about the nature of the active site (shape, polarity, size, etc.) Write your conclusions.
Pyroglutaryl-peptidase II, PPII, is an ectopeptidase (enzyme) that serves as an important role in the regulation of the biologically active thyrotropin-releasing hormone, TRH. It acts by cleaving the terminal pyroglutamic acid (Glp) from TRH, [Glp-His-ProNH2, pyroglutamyl-histidyl-prolineamide]. The enzyme does not cleave any other peptides that contain a terminal Glp residue, thereby displaying significant substrate specificity toward TRH with a Km value of 35 a) Sketch a graph of 1/vo vs. 1/[S] for the 4 different compounds (labeling each line 1-4). Label the relevant points on your sketch that are expected given the information provided about the compounds. b) Compare the compounds 2,3, and 4 with the normal substrate and draw conclusions about the nature of the active site (shape, polarity, size, etc.) Write your conclusions. Mu M. Since the action of TRH in the central nervous system (CNS) can be beneficial for treatment of certain CNS disorders, such as epilepsy and memory loss, selective inhibition of PPII could serve to modulate the active levels of TRH. To date there is no experimental structure for PPII on which to base the rational design of active site directed inhibitors. Therefore a series of competitive inhibitors have been designed and tested.Explanation / Answer
Enzymic degradation plays an important role in the regulation of biologically active peptides . Extracellularly oriented, membrane-associated peptidases (ectopeptidases), in particular, are strategically located to terminate peptide-mediated cell signalling . It is apparent that a relatively small number of ectopeptidases with broad specificities provide a key mechanism for controlling the levels of a large number of peptides .
PPII (pyroglutamyl-peptidase II) (EC 3.4.19.6), also known as TRH (thyrotropin-releasing hormone)-degrading ectoenzyme, is a highly unusual ectopeptidase in that it appears to display absolute functional specificity for its substrate, TRH [or Glp-His-ProNH2 (pyroglutamyl-histidyl-prolineamide)] [6
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