List six drugs and six enzyme for uncompetitive inhibitors.
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uncompetitive enzyme inhibitor drugs examples clinical pharmacology
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uncompetitive inhibitors drug examples metformin lithium memantine AHAS herbicides enzymes
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https://en.wikipedia.org/wiki/Uncompetitive_inhibition
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Here is a well-organized reference table of six drugs and six enzymes involved in uncompetitive inhibition:
Six Drugs That Act as Uncompetitive Inhibitors
| # | Drug | Target Enzyme | Clinical Use |
|---|---|---|---|
| 1 | Lithium | Inositol monophosphatase (IMPase) | Bipolar disorder - the "lithium paradox" is a textbook example of uncompetitive inhibition; inhibition is stronger at higher substrate concentrations |
| 2 | Memantine | NMDA receptor (glutamate-gated ion channel) | Alzheimer's disease - binds only the open, substrate-occupied (Mg²⁺-displaced) receptor channel |
| 3 | Metformin | Mitochondrial Complex I (NADH dehydrogenase) | Type 2 diabetes - uncompetitively inhibits NADH:ubiquinone oxidoreductase, reducing hepatic gluconeogenesis |
| 4 | Brefeldin A | ADP-ribosylation factor (ARF) GEF (e.g., Sec7 domain proteins) | Research tool / antiviral - traps the ARF-GDP-GEF ternary complex, a classic ES-complex-only inhibition model |
| 5 | Tertiary amines (e.g., choline) | Acetylcholinesterase (AChE) | Neuropharmacology - bind only the acylated (ES) intermediate of AChE, not free enzyme (cited in Henry's Clinical Diagnosis textbook) |
| 6 | AHAS inhibitors (e.g., imazethapyr, sulfometuron methyl) | Acetohydroxyacid synthase (AHAS) | Herbicides - uncompetitively inhibit the enzyme with respect to pyruvate, blocking branched-chain amino acid synthesis in plants |
Six Enzymes Commonly Subject to Uncompetitive Inhibition
| # | Enzyme | Pathway/Function | Example Inhibitor |
|---|---|---|---|
| 1 | Inositol monophosphatase (IMPase) | Phosphoinositide signaling cycle | Lithium ions (Li⁺) |
| 2 | NMDA receptor (ion channel complex) | Glutamatergic synaptic transmission | Memantine, MK-801 |
| 3 | Mitochondrial Complex I (NADH dehydrogenase) | Oxidative phosphorylation, electron transport chain | Metformin |
| 4 | ARF guanine nucleotide exchange factor (Sec7/ARNO) | Golgi membrane trafficking | Brefeldin A |
| 5 | Acetylcholinesterase (AChE) | Hydrolysis of acetylcholine at nerve synapses | Tertiary amines (choline), some carbamates |
| 6 | Acetohydroxyacid synthase (AHAS) | Branched-chain amino acid biosynthesis | Sulfonylurea and imidazolinone herbicides |
Key Kinetic Features of Uncompetitive Inhibition (quick recap)
- The inhibitor binds only to the enzyme-substrate (ES) complex - not free enzyme
- Both Vmax and Km decrease proportionally (the ratio Vmax/Km, or catalytic efficiency, stays the same)
- Lineweaver-Burk plot shows parallel lines (same slope, higher y-intercept) compared to uninhibited enzyme
- Inhibition is paradoxically stronger at high substrate concentrations - this is exploited therapeutically by lithium, since IMPase is most active in highly stimulated (manic) neurons
- Diluting the specimen/substrate will diminish or abolish the effect, as noted in Henry's Clinical Diagnosis and Management by Laboratory Methods
Sources:
- Henry's Clinical Diagnosis and Management by Laboratory Methods, section on Uncompetitive Inhibition
- Wikipedia - Uncompetitive inhibition (with Nahorski et al. 1991 on lithium/IMPase, PMID 1658998)
- Enzyme Inhibitors as Multifaceted Tools in Medicine and Agriculture (PMC11433695)
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