i synthesis Ul laulolabeled carbon into sterols Substrate Mevastatin (nM) Incorp
ID: 257352 • Letter: I
Question
i synthesis Ul laulolabeled carbon into sterols Substrate Mevastatin (nM) Incorporation into Sterols (cpmlmg protein) 13770 10080 4120 8270 6020 2410 1050 570 270 35870 34940 34180 0 4C-acetate (100) 73 30 (100) 73 29 (100) 54 26 (100) 97 95 50 0 C-acetyl-CoA 50 4C-HMG-CoA 50 0 14C-Mevalonate of experiments, the radiolabeled precursor listed was incubated with rat liver lysates (broken celly). The ction mixture in each case contained 1 mM ATR 10 mM glucose-1-phosphate, 6 mM glutathione, 6 mM MgCl 40 ?? CoA, 0.25 mMINAD, 0.25 mNIN proteins. Reactions were incubated for 60 min at 37'C, then the reaction was terminated by the adition of KOH. Lipids were extracted from the mixture and subjected to scintillation counting (measured in cpm (counts per minutel) to determine the amount of radiolabel incorporated into cholesterol. Adapted from Endo, Kuroda, and Tazawa [Ref. 6 100 mM potassium phosphate buffer pH 7.4, and 1.65 mg rat liver Question 6. The data in Table 3 allowed the authors to zero in on which enzyme was the drug target. Looking back at Figure 4 (the reaction pathway from acetyl-CoA), which enzyme is likely to be the target of mevastatinExplanation / Answer
Mevastatin at 0 nM in C-HMG-CoA has a 1050 cpm/mg protein. At 5nM 46% activity is decreased. so it is strong inhibitor for Mevastatin.
Mevastatin is a competitive inhibitor of HMG-Coenzyme A (HMG-CoA) reductase with a binding affinity 10,000 times greater than the HMG-CoA substrate itself.
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