Direction: HMGCoA reductase that binds HMGCoA, is the major rate limiting step in the cholesterol biosynthetic pathway. Several inhibitors of this enzyme are used as potential drugs. The assay of the enzyme is based on labeling the enzyme with radiolabeled HMGCoA and counting (cpm) the labeled enzyme substrate complex in the presence (test) and in the absence (control) of the inhibitor. A bland is set up that contains no enzyme.
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The percent inhibition for this enzyme is calculated from the equation
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- {[cpm (control) – cpm (test)]/[cpm (control) – cpm (blank)]} × 100
- {[cpm (control) – cpm (test)]/[cpm(blank) – cpm (control)])} × 100
- {[cpm (test) – cpm (control)]/[cpm (control) – cpm (blank)])} × 100
- {[cpm (control) – cpm (blank)]/[cpm (test) – cpm (control)])} × 100
Correct Option: A
The amount of radioactivity will be in order
control >test > blank
| % inhibition = | ||
| control - blank |
| decrease in enzyme complex = | = complex formation in absence of inhibitor | |
| maxmimum enzyme- substrate |
