Moof's Medical Biochemistry Video Course: moof-university.thinkific.com/...
Questions Answered in This Video:
- What are competitive inhibitors, and what is mechanism by which they act?
- How do competitive inhibitors affect the values of KM and VMAX?
- How do competitively inhibited reactions look on the hyperbolic graph and Lineweaver-Burk plot?
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Video Content Summary:
Competitive inhibitors "compete" with substrate for binding the enzyme's active site. Free enzyme will bind either the substrate OR the competitive inhibitor. It cannot bind both at the same time. If the enzyme binds the substrate, the enzyme-substrate complex forms, and the enzyme can convert the substrate into product. If, however, a competitive inhibitor binds the active site, the enzyme-competitive inhibitor complex forms, which cannot proceed towards products, for the simple reason that the competitive inhibitor impedes the ability of the substrate to bind to the enzyme.
Since a competitive inhibitor blocks the substrate from binding, the competitive inhibitor essentially lowers the affinity of enzyme for the substrate. Thus increasing the KM. Despite this, VMAX can still be reached with a high enough substrate concentration. If the substrate concentration is sufficiently high, the substrates will out-compete the competitive inhibitor for binding at the active site, thus effectively overcoming the effects of the inhibitor.
The effects of a competitive inhibitor on an enzyme-catalyzed reaction are depicted in a variety of ways in the video, and it is shown what happens to the hyperbolic graph and the Lineweaver-Burk plot, otherwise known as the double reciprocal plot.