# Structural Biochemistry/Enzyme/Noncompetitive Inhibitor

**E + I − (through a substrate) → ES + I → E + P**

**ES + I ⇌ ESI → NR (no reaction)**

where E is enzyme, I is inhibitor, ES is enzyme-substrate complex, P is product. ESI is the molecule after the inhibitor is bound to the enzyme-substrate complex. ESI cannot form any products, so the later reaction is not allowed (or, no reaction).

Based on the Michaelis-Menten Model, K_{M}, the concentration of the substrate when the velocity is the half of the maximum velocity (or half of the substrates at maximum velocity), remains same, but the maximum velocity is decreased.

The picture shows a double-reciprocal plot of V_{0} and [S]. The x-intercept is equal to -1/K_{m} while the y-intercept is 1/V_{max}. The slope of the line is K_{m}/V_{max}. Thus, the plot shows that there is no change in K_{m} and V_{max} is decreased. In relation to the original plot, the x intercept stays constant while the y intercept increases along with the slope.

File:Noncompetitive inhibitor.jpg

## References[edit]

Berg, Jeremy M., John L. Tymoczko, and Lubert Stryer. BIOCHEMISTRY. 6th ed. New York: W. H. FREEMAN AND COMPANY, 2007.

Reece, Jane (2011). *Biology*. Pearson. ISBN 978-0-321-55823-7.