Lipitor, a medication used to treat high cholesterol, works by binding to HMG CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body. This binding process inhibits the function of HMG CoA reductase, which in turn reduces the production of cholesterol, thereby helping to lower the individual's cholesterol levels.

The active ingredient in Lipitor, atorvastatin, is a competitive inhibitor of HMG CoA reductase. This means that atorvastatin binds to the same active site on the enzyme as the substrate, HMG CoA, but with a higher affinity. As a result, atorvastatin prevents HMG CoA from binding and being reduced to mevalonate, a key intermediate in the cholesterol biosynthesis pathway.

The binding of atorvastatin to HMG CoA reductase is a reversible process, allowing for the possibility of dissociation and the resumption of enzyme function if atorvastatin levels in the body decrease. However, the high affinity of atorvastatin for the enzyme ensures that the inhibition of HMG CoA reductase is maintained, leading to a significant reduction in cholesterol production.

In summary, Lipitor binds to HMG CoA reductase through its active ingredient, atorvastatin, which competitively inhibits the enzyme's function by binding to the same active site as the substrate. This binding process reduces the production of cholesterol and helps to manage high cholesterol levels.

Sources:

1. [DrugPatentWatch.com - Lipitor (Atorvastatin)](https://www.drugpatentwatch.com/drugs/lipitor)
2. [NCBI - Atorvastatin: a review of its use in the treatment of hypercholesterolemia and dyslipidemia](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2659777/)
3. [British Journal of Clinical Pharmacology - Mechanism of action of HMG-CoA reductase inhibitors ("statins")](https://bpspubs.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2125.2004.02041.x)