Target type: biologicalprocess
The process of transferring reducing equivalents from the cytosol into the mitochondria; NADH is used to synthesise malate in the cytosol; this compound is then transported into the mitochondria where it is converted to oxaloacetate using NADH, the oxaloacetate reacts with gluamate to form aspartate, and the aspartate then returns to the cytosol to complete the cycle. [GOC:jl, GOC:mtg_electron_transport, ISBN:0716743663]
The malate-aspartate shuttle is a metabolic pathway that facilitates the transfer of reducing equivalents (electrons) from the cytosol to the mitochondria. This process is essential for ATP production during aerobic respiration, particularly in tissues with high energy demands like the heart and liver. Here’s a detailed breakdown:
1. **NADH Generation in the Cytosol:** In the cytosol, NADH is produced through glycolysis and other metabolic reactions. However, NADH cannot directly cross the mitochondrial membrane.
2. **Oxaloacetate Reduction to Malate:** The malate-aspartate shuttle utilizes oxaloacetate, a four-carbon molecule present in the cytosol. NADH reduces oxaloacetate to malate using the enzyme malate dehydrogenase.
3. **Malate Transport into Mitochondria:** Malate can readily cross the mitochondrial membrane via a specific transporter.
4. **Malate Oxidation to Oxaloacetate in the Mitochondrial Matrix:** Inside the mitochondrial matrix, malate is oxidized back to oxaloacetate by another malate dehydrogenase, this time coupled with the reduction of NAD+ to NADH. This NADH generated within the mitochondria can now directly participate in the electron transport chain.
5. **Oxaloacetate Conversion to Aspartate:** To regenerate oxaloacetate in the cytosol, it is converted to aspartate by transamination. This reaction involves the transfer of an amino group from glutamate to oxaloacetate, catalyzed by the enzyme aspartate aminotransferase.
6. **Aspartate Transport into the Cytosol:** Aspartate, unlike oxaloacetate, can also cross the mitochondrial membrane via a specific transporter.
7. **Aspartate Conversion to Oxaloacetate in the Cytosol:** In the cytosol, aspartate is reconverted to oxaloacetate by transamination, regenerating the starting molecule for the shuttle.
8. **Shuttle Completion:** The cycle repeats as malate is produced again, and the process continues to transfer reducing equivalents from the cytosol to the mitochondria.
This shuttle system effectively bypasses the impermeability of the mitochondrial membrane to NADH, enabling the efficient utilization of reducing equivalents generated in the cytosol for oxidative phosphorylation and ATP synthesis.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| Malate dehydrogenase, mitochondrial | A malate dehydrogenase, mitochondrial that is encoded in the genome of human. [PRO:DNx, UniProtKB:P40926] | Homo sapiens (human) |
| Malate dehydrogenase, cytoplasmic | A malate dehydrogenase, cytoplasmic that is encoded in the genome of human. [PRO:DNx, UniProtKB:P40925] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| benzyl benzoate | benzyl benzoate : A benzoate ester obtained by the formal condensation of benzoic acid with benzyl alcohol. It has been isolated from the plant species of the genus Polyalthia. benzyl benzoate: structure; acarosan, a moist powder composed of wetted cellulose and benzyl benzoate, is used on carpets as an acaricide | benzoate ester; benzyl ester | acaricide; plant metabolite; scabicide |
| clotrimazole | conazole antifungal drug; imidazole antifungal drug; imidazoles; monochlorobenzenes | antiinfective agent; environmental contaminant; xenobiotic | |
| econazole | 1-{2-(4-chlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl}imidazole : A member of the class of imidazoles that is 1-(2,4-dichlorophenyl)-2-(imidazol-1-yl)ethanol in which the hydroxyl hydrogen is replaced by a 4-chlorobenzyl group. econazole : A racemate composed of equimolar amounts of (R)- and (S)-econazole. Used (as its nitrate salt) to treat skin infections such as athlete's foot, jock itch, ringworm and other fungal skin infections. Econazole: An imidazole derivative that is commonly used as a topical antifungal agent. | dichlorobenzene; ether; imidazoles; monochlorobenzenes | |
| fluconazole | fluconazole : A member of the class of triazoles that is propan-2-ol substituted at position 1 and 3 by 1H-1,2,4-triazol-1-yl groups and at position 2 by a 2,4-difluorophenyl group. It is an antifungal drug used for the treatment of mucosal candidiasis and for systemic infections including systemic candidiasis, coccidioidomycosis, and cryptococcosis. Fluconazole: Triazole antifungal agent that is used to treat oropharyngeal CANDIDIASIS and cryptococcal MENINGITIS in AIDS. | conazole antifungal drug; difluorobenzene; tertiary alcohol; triazole antifungal drug | environmental contaminant; P450 inhibitor; xenobiotic |
| glyburide | glyburide : An N-sulfonylurea that is acetohexamide in which the acetyl group is replaced by a 2-(5-chloro-2-methoxybenzamido)ethyl group. Glyburide: An antidiabetic sulfonylurea derivative with actions like those of chlorpropamide | monochlorobenzenes; N-sulfonylurea | anti-arrhythmia drug; EC 2.7.1.33 (pantothenate kinase) inhibitor; EC 3.6.3.49 (channel-conductance-controlling ATPase) inhibitor; hypoglycemic agent |
| ketoconazole | 1-acetyl-4-(4-{[2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy}phenyl)piperazine : A dioxolane that is 1,3-dioxolane which is substituted at positions 2, 2, and 4 by imidazol-1-ylmethyl, 2,4-dichlorophenyl, and [para-(4-acetylpiperazin-1-yl)phenoxy]methyl groups, respectively. | dichlorobenzene; dioxolane; ether; imidazoles; N-acylpiperazine; N-arylpiperazine | |
| mefenamic acid | mefenamic acid : An aminobenzoic acid that is anthranilic acid in which one of the hydrogens attached to the nitrogen is replaced by a 2,3-dimethylphenyl group. Although classed as a non-steroidal anti-inflammatory drug, its anti-inflammatory properties are considered to be minor. It is used to relieve mild to moderate pain, including headaches, dental pain, osteoarthritis and rheumatoid arthritis. Mefenamic Acid: A non-steroidal anti-inflammatory agent with analgesic, anti-inflammatory, and antipyretic properties. It is an inhibitor of cyclooxygenase. | aminobenzoic acid; secondary amino compound | analgesic; antipyretic; antirheumatic drug; EC 1.14.99.1 (prostaglandin-endoperoxide synthase) inhibitor; environmental contaminant; non-steroidal anti-inflammatory drug; xenobiotic |
| miconazole | 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]imidazole : A member of the class of imidazoles that is 1-(2,4-dichlorophenyl)-2-(imidazol-1-yl)ethanol in which the hydroxyl hydrogen is replaced by a 2,4-dichlorobenzyl group. miconazole : A racemate composed of equimolar amounts of (R)- and (S)-miconazole. Used (as its nitrate salt) to treat skin infections such as athlete's foot, jock itch, ringworm and other fungal skin infections. It inhibits the synthesis of ergosterol, a critical component of fungal cell membranes. Miconazole: An imidazole antifungal agent that is used topically and by intravenous infusion. | dichlorobenzene; ether; imidazoles | |
| nicardipine | 2-[benzyl(methyl)amino]ethyl methyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate : A dihydropyridine that is 1,4-dihydropyridine substituted by a methyl, {2-[benzyl(methyl)amino]ethoxy}carbonyl, 3-nitrophenyl, methoxycarbonyl and methyl groups at positions 2, 3, 4, 5 and 6, respectively. nicardipine : A racemate comprising equimolar amounts of (R)- and (S)-nicardipine. It is a calcium channel blocker which is used to treat hypertension. Nicardipine: A potent calcium channel blockader with marked vasodilator action. It has antihypertensive properties and is effective in the treatment of angina and coronary spasms without showing cardiodepressant effects. It has also been used in the treatment of asthma and enhances the action of specific antineoplastic agents. | benzenes; C-nitro compound; diester; dihydropyridine; methyl ester; tertiary amino compound | |
| oxaprozin | oxaprozin : A monocarboxylic acid that is a propionic acid derivative having a 4,5-diphenyl-1,3-oxazol-2-yl substituent at position 3. It is non-steroidal anti-inflammatory drug commonly used to relieve the pain and inflammatory responses associated with osteoarthritis and rheumatoid arthritis. Oxaprozin: An oxazole-propionic acid derivative, cyclooxygenase inhibitor, and non-steroidal anti-inflammatory drug that is used in the treatment of pain and inflammation associated with of OSTEOARTHRITIS; RHEUMATOID ARTHRITIS; and ARTHRITIS, JUVENILE. | 1,3-oxazoles; monocarboxylic acid | analgesic; non-steroidal anti-inflammatory drug |
| sulconazole | 1-{2-[(4-chlorobenzyl)sulfanyl]-2-(2,4-dichlorophenyl)ethyl}-1H-imidazole : A member of the class of imidazoles that is 1-ethyl-1H-imidazole in which one of the hydrogens of the methyl group is replaced by a (4-chlorobenzyl)sulfanediyl group while a second is replaced by a 2,4-dichlorophenyl group. sulconazole : A racemate comprising equimolar amounts of (R)- and (S)-sulconazole. An antifungal agent with activity against Candida species, it is used (generally as the nitrate salt) for the topical treatment of fungal skin infections. sulconazole: RN given refers to cpd with unspecified isomeric designation; structure given in first source | dichlorobenzene; imidazoles; monochlorobenzenes; organic sulfide | |
| delavirdine | delavirdine : The amide resulting from the formal condensation of 5-[(methylsulfonyl)amino]-1H-indole-2-carboxylic acid and 4-amino group of 1-[3-(isopropylamino)pyridin-2-yl]piperazine, delavirdine is a non-nucleoside reverse transcriptase inhibitor with activity specific for HIV-1. Viral resistance emerges rapidly when delavirdine is used alone, so it is therefore used (as the methanesulfonic acid salt) with other antiretrovirals for combination therapy of HIV infection. Delavirdine: A potent, non-nucleoside reverse transcriptase inhibitor with activity specific for HIV-1. | aminopyridine; indolecarboxamide; N-acylpiperazine; sulfonamide | antiviral drug; HIV-1 reverse transcriptase inhibitor |
| thyroxine | thyroxine : An iodothyronine compound having iodo substituents at the 3-, 3'-, 5- and 5'-positions. Thyroxine: The major hormone derived from the thyroid gland. Thyroxine is synthesized via the iodination of tyrosines (MONOIODOTYROSINE) and the coupling of iodotyrosines (DIIODOTYROSINE) in the THYROGLOBULIN. Thyroxine is released from thyroglobulin by proteolysis and secreted into the blood. Thyroxine is peripherally deiodinated to form TRIIODOTHYRONINE which exerts a broad spectrum of stimulatory effects on cell metabolism. | 2-halophenol; iodophenol; L-phenylalanine derivative; non-proteinogenic L-alpha-amino acid; thyroxine; thyroxine zwitterion | antithyroid drug; human metabolite; mouse metabolite; thyroid hormone |