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Competitive inhibition can be overcome by adding more substrate to the reaction, which increases the chances of the enzyme and substrate binding. As a result, competitive inhibition alters only the K m, leaving the V max the same. [3] This can be demonstrated using enzyme kinetics plots such as the Michaelis–Menten or the Lineweaver-Burk plot.
Effects of different types of inhibition on the double-reciprocal plot. When used for determining the type of enzyme inhibition, the Lineweaver–Burk plot can distinguish between competitive, pure non-competitive and uncompetitive inhibitors. The various modes of inhibition can be compared to the uninhibited reaction.
For example, an inhibitor might compete with substrate A for the first binding site, but be a non-competitive inhibitor with respect to substrate B in the second binding site. [ 26 ] Traditionally reversible enzyme inhibitors have been classified as competitive, uncompetitive, or non-competitive, according to their effects on K m and V max . [ 14 ]
This can be competitive inhibition, uncompetitive inhibition, non-competitive inhibition or partially competitive inhibition. If the molecule induces enzymes that are responsible for its own metabolism, this is called auto-induction (or auto-inhibition if there is inhibition).
Substrate analogs can act as competitive inhibitors of an enzymatic reaction. An example is phosphoramidate to the Tetrahymena group I ribozyme. [1] Other examples of substrate analogs include 5’-adenylyl-imidodiphosphate, a substrate analog of ATP, and 3-acetylpyridine adenine dinucleotide, a substrate analog of NADH. [2]
It is a competitive inhibitor of all three 5α-reductase isoenzymes [4] and it inhibits types 1 and 2 better than finasteride, leading to it causing further reduction in DHT, with >90% reduced DHT levels following 1 year of oral administration. [1] Epristeride is the third marketed steroidal 5-ARI. It is a noncompetitive, specific inhibitor.
The drugs are structurally similar to vitamin K and act as competitive inhibitors of the enzyme. The term "vitamin K antagonist" is a misnomer , as the drugs do not directly antagonise the action of vitamin K in the pharmacological sense, but rather the recycling of vitamin K.
Two equations listed below that are referred to as non-competitive substrate inhibition and competitive substrate inhibition models respectively by Shuler and Michael in Bioprocess Engineering: Basic Concepts. Note that the Haldane equation above is a special case of the following non-competitive substrate inhibition model, where KI >>Ks. [1]