Knowledge Bank

Overview

Catalase is one of the most catalytically efficient enzymes known, decomposing millions of hydrogen peroxide molecules per second. Present predominantly in peroxisomes, it prevents H2O2 accumulation and protects cells from oxidative damage, working synergistically with SOD.

Mechanism of Action

Catalase is a heme-enzyme that catalyzes the reaction 2H₂O₂ → 2H₂O + O₂. The reaction proceeds when H₂O₂ oxidizes the enzyme's iron center to Compound I, a high-valent iron intermediate; a second H₂O₂ molecule then reduces this intermediate. Operating at an exceptionally high turnover, catalase prevents accumulation of H₂O₂ that could otherwise generate hydroxyl radicals.

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Glutathione peroxidase (GPx) is a selenium-containing enzyme family that reduces lipid hydroperoxides and H2O2 using glutathione as the electron donor. GPx plays a critical role in protecting cellular membranes from oxidative damage and maintaining intracellular redox balance.

Mechanism of Action

Glutathione Peroxidase (GPx) is a selenoprotein containing selenocysteine at its active site. It reduces H₂O₂ and lipid hydroperoxides to their corresponding alcohols, using glutathione (GSH) as the reducing agent. The GPx4 isoform directly reduces complex lipid peroxides and has been identified as a regulator of ferroptosis.

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Bromelain is a cysteine protease complex derived from pineapple stem (Ananas comosus). It exerts potent anti-inflammatory effects by inhibiting NF-κB and COX-2 pathways, while displaying fibrinolytic activity and providing proteolytic digestive support.

Mechanism of Action

Bromelain is a cysteine protease complex derived from pineapple stem (Ananas comosus). It inhibits NF-κB and MAPK signaling pathways, suppressing iNOS and COX-2 expression and reducing production of pro-inflammatory cytokines. It also modulates the arachidonate cascade, inhibits platelet aggregation, and displays fibrinolytic activity.

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Lysozyme (muramidase) is a glycoside hydrolase enzyme that disrupts bacterial peptidoglycan layers, causing bacterial lysis. Abundantly present in tears, saliva, and human milk, it is a key antimicrobial component of the innate immune system.

Mechanism of Action

Lysozyme (muramidase) is a glycoside hydrolase enzyme that cleaves β-(1,4)-glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine. This disrupts bacterial peptidoglycan layers, compromising cell wall integrity and causing bacterial lysis. As a cationic antimicrobial peptide, it also provides a second defense mechanism independent of its muramidase activity.

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Glutathione-S-Transferase (GST) is an enzyme family that conjugates glutathione to electrophilic xenobiotics, increasing their water solubility and facilitating excretion. It is critically important in cancer chemoprevention and multidrug resistance research.

Mechanism of Action

Glutathione-S-Transferase (GST) is a family of enzymes that catalyze the conjugation of glutathione (GSH) to electrophilic xenobiotics generated by cytochrome P450 metabolism. An active-site residue activates GSH to the nucleophilic GS⁻ form; this nucleophile forms conjugates with carcinogens and environmental pollutants, increasing water solubility and facilitating excretion.

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Telomerase is a ribonucleoprotein complex consisting of the TERT reverse transcriptase subunit and the RNA component TERC. It maintains telomere length by adding TTAGGG repeats to chromosome ends; it is active in stem cells and cancer cells and is a central regulator of aging biology.

Mechanism of Action

Telomerase is a ribonucleoprotein complex consisting of the TERT (reverse transcriptase subunit) and the RNA component TERC. It maintains telomere length by adding TTAGGG repeats to chromosome ends, thereby delaying cellular senescence. In cancer cells, telomerase is reactivated through TERT promoter mutations or epigenetic activation.

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Vitamin B12 (cobalamin) is a water-soluble vitamin essential for two key enzymes: methionine synthase, involved in DNA methylation and homocysteine regulation, and L-methylmalonyl-CoA mutase, involved in fatty acid metabolism. Deficiency leads to megaloblastic anemia and irreversible neurological damage.

Mechanism of Action

Vitamin B12 (cobalamin) is a cofactor for methionine synthase, catalyzing the synthesis of methionine from homocysteine and thereby supporting production of S-adenosylmethionine (SAM), the universal methyl donor. SAM is essential for virtually all transmethylation reactions including DNA, RNA, histone, and neurotransmitter methylation.

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Vitamin D3 (cholecalciferol) is a fat-soluble prohormone synthesized in skin upon UV-B exposure. After hepatic and renal hydroxylation to active calcitriol, it functions as a steroid hormone binding nuclear vitamin D receptors and regulating expression of over 1,000 genes across virtually all tissues.

Mechanism of Action

Vitamin D3 (cholecalciferol) is converted in the liver to 25(OH)D3, then by renal and immune cells to the active form 1,25(OH)₂D3 (calcitriol). Calcitriol binds the vitamin D receptor (VDR), heterodimerizes with the retinoid X receptor, and regulates transcription of thousands of genes; it enhances intestinal calcium absorption and modulates immune pathways.

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The B-complex encompasses eight water-soluble vitamins — B1, B2, B3, B5, B6, B7, B9, and B12 — that collectively act as coenzymes in cellular energy metabolism, DNA synthesis, neurotransmitter production, and one-carbon metabolic pathways.

Mechanism of Action

The B vitamin complex (B1, B2, B3, B5, B6, B7, B9, B12) is a group of water-soluble vitamins functioning as coenzymes in mitochondrial aerobic respiration. Their active forms (thiamine pyrophosphate, FAD, NAD+, coenzyme A) catalyze critical steps in the citric acid cycle and electron transport chain for ATP production.

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Vitamin A regulates cell differentiation and proliferation genes through its active form all-trans retinoic acid (atRA) via RAR/RXR nuclear receptors. In its 11-cis-retinal form it is essential for photoreceptor function, and it plays critical roles in immune development and epithelial integrity.

Mechanism of Action

Vitamin A regulates gene expression through its active form all-trans retinoic acid (atRA) via nuclear receptors (RAR/RXR heterodimers). This complex binds retinoic acid response elements in DNA to modulate transcription of genes governing cell differentiation and proliferation. Retinol in its 11-cis-retinal form is also essential for photoreceptor function.

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Vitamin E (α-tocopherol) acts as a chain-breaking antioxidant within lipophilic biological membranes and lipoproteins. It terminates lipid peroxidation chain reactions and is regenerated by vitamin C or glutathione, completing the antioxidant cycle.

Mechanism of Action

Vitamin E (α-tocopherol) acts as a chain-breaking antioxidant within lipophilic biological membranes and lipoproteins. It terminates lipid peroxidation chain reactions by donating a hydrogen atom to lipid peroxyl radicals; the resulting tocopheroxyl radical is regenerated by vitamin C or glutathione.

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Vitamin K2 (menaquinone, especially MK-7) activates osteocalcin and matrix Gla protein as a cofactor for gamma-glutamyl carboxylase. Osteocalcin supports calcium deposition in bone while matrix Gla protein prevents calcification in vessel walls.

Mechanism of Action

Vitamin K2 (menaquinone, especially MK-7) is a cofactor for gamma-glutamyl carboxylase, which γ-carboxylates glutamate residues of vitamin K-dependent proteins. This carboxylation activates the calcium-binding capacity of osteocalcin and matrix Gla protein; osteocalcin supports calcium deposition in bone, while matrix Gla protein inhibits vascular calcification.

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Folate (vitamin B9) is the central cofactor of one-carbon metabolism. Its tetrahydrofolate form supports purine and thymidine synthesis and methionine recycling, providing methyl groups for DNA and histone methylation via SAM production.

Mechanism of Action

Folate (vitamin B9) is the central cofactor of one-carbon metabolism. Its tetrahydrofolate (THF) form carries single-carbon units to support thymidine and purine synthesis and methionine recycling, thereby generating SAM to provide methyl groups for DNA and histone methylation. Inadequate folate disrupts the nucleotide pool and leads to DNA hypomethylation.

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L-Arginine is a semi-essential amino acid and the exclusive precursor for nitric oxide synthesis via nitric oxide synthase enzymes. NO regulates vascular tone, platelet aggregation, and immune function. Arginine also stimulates growth hormone secretion and serves as a key intermediate in the urea cycle.

Mechanism of Action

L-Arginine is the direct precursor for nitric oxide (NO) synthesis as the substrate for endothelial nitric oxide synthase (eNOS). eNOS converts L-arginine to L-citrulline, generating NO; NO activates guanylate cyclase to increase cGMP, leading to smooth muscle relaxation and vasodilation. It also inhibits platelet aggregation and participates in the urea cycle.

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Taurine is a conditionally essential sulfur-containing amino acid abundantly present in the heart, skeletal muscle, retina, and CNS. It regulates intracellular calcium signaling, osmotic balance, and bile acid conjugation, while exerting broad antioxidant and anti-inflammatory effects.

Mechanism of Action

Taurine supports mitochondrial protein synthesis by forming 5-taurinomethyluridine on mitochondrial tRNA, enhancing electron transport chain activity. It limits cellular damage by directly scavenging hypochlorous acid and preventing calcium overload, and regulates blood pressure by increasing nitric oxide bioavailability.

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Glycine is the simplest amino acid, constituting approximately 33% of all collagen residues. It acts as an inhibitory neurotransmitter at glycine receptors in the brainstem and spinal cord, and plays essential roles in glutathione synthesis, one-carbon metabolism, and liver detoxification.

Mechanism of Action

Glycine is the dominant amino acid in the collagen Gly-X-Y repeat motif, determining triple helix stability; adequate glycine is essential for cartilage and connective tissue synthesis. In sleep regulation it activates NMDA receptors to induce peripheral vasodilation and a drop in core body temperature; as a neurotransmitter it participates in spinal cord inhibition.

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Carnosine is an endogenous dipeptide (beta-alanine + L-histidine) highly concentrated in muscle and brain. It serves as an intracellular pH buffer during high-intensity exercise, a carbonyl scavenger inhibiting advanced glycation end-product formation, and a zinc and copper chelator.

Mechanism of Action

Carnosine (β-alanyl-L-histidine) is a dipeptide found at high concentrations in skeletal muscle. The pKa of histidine's imidazole ring provides muscle pH buffering, delaying fatigue by balancing lactic acid accumulation during intense exercise. Through non-enzymatic reaction with protein carbonyl groups it prevents advanced glycation end product (AGE) formation and chelates metal ions.

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Lysine is an essential amino acid that contributes to the indispensable post-translational modification enabling collagen fibril formation by generating hydroxylysine in procollagen. It is also the precursor for carnitine synthesis, supporting mitochondrial fatty acid oxidation.

Mechanism of Action

Lysine serves as the substrate for prolyl hydroxylase and lysyl hydroxylase enzymes, generating hydroxylysine in procollagen; this post-translational modification is essential for collagen cross-linking and fibril formation. Lysine is also a precursor amino acid for carnitine synthesis, supporting mitochondrial fatty acid oxidation.

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Cysteine is the rate-limiting amino acid for glutathione biosynthesis; its N-acetylcysteine (NAC) form is the most widely used clinical glutathione precursor. Through the redox state of protein thiol groups it regulates enzyme activities, signaling pathways, and cellular redox homeostasis.

Mechanism of Action

Cysteine is the rate-limiting amino acid for glutathione biosynthesis. The enzyme glutamate-cysteine ligase combines cysteine with glutamate to form γ-glutamylcysteine; GSH synthase then adds glycine to produce glutathione (GSH). The redox state of protein thiol groups determines their tertiary structure and function.

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Tyrosine is the central precursor for catecholamine neurotransmitter synthesis, converted by tyrosine hydroxylase to dopamine, then norepinephrine and epinephrine. It also serves as the building block for thyroid hormone synthesis.

Mechanism of Action

Tyrosine is the central precursor for catecholamine neurotransmitter synthesis, converted by tyrosine hydroxylase to L-DOPA and then to dopamine, norepinephrine, and epinephrine. It is also used in thyroid hormone synthesis; iodination forms the building blocks of thyroxine (T4) and triiodothyronine (T3).

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Tryptophan is the sole dietary precursor for serotonin and melatonin biosynthesis. It is also converted to NAD+ precursor nicotinamide nucleotides via the kynurenine pathway; it regulates the gut-brain axis, mood, the sleep-wake cycle, and immune responses.

Mechanism of Action

Tryptophan converts a portion of dietary intake to serotonin (5-HT) and then melatonin via the serotonin/melatonin pathway, and the majority to nicotinamide nucleotides (NAD+ precursors) via the kynurenine pathway. Serotonin regulates the gut-brain axis, affecting mood, the sleep-wake cycle, and gut motility.

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Proline frequently occupies the X and Y positions of the Gly-X-Y motif in collagen and is converted to hydroxyproline by prolyl 4-hydroxylase to increase collagen triple helix thermal stability. It also modulates oxidative stress responses via the proline cycle.

Mechanism of Action

Proline frequently occupies the X and Y positions of the Gly-X-Y motif in collagen and is converted to hydroxyproline in procollagen by prolyl 4-hydroxylase. This hydroxylation increases the thermal stability of the collagen triple helix and reinforces tissue integrity. Proline also modulates cellular responses to oxidative stress via the 'proline cycle.'

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Flavin adenine dinucleotide (FAD) is a redox-active coenzyme synthesized from riboflavin (vitamin B2). It serves as a prosthetic group for flavoproteins and participates in the mitochondrial electron transport chain, beta-oxidation of fatty acids, and the TCA cycle.

Mechanism of Action

FAD (flavin adenine dinucleotide) is a riboflavin (B2)-derived coenzyme that catalyzes single- or two-electron redox reactions via its isoalloxazine ring. As a component of mitochondrial Complex II, it catalyzes the oxidation of succinate to fumarate and transfers electrons to coenzyme Q10, linking fatty acid β-oxidation to the respiratory chain.

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Coenzyme Q10 (ubiquinone) is a fat-soluble molecule present in virtually every cell. As a mobile electron carrier in the mitochondrial inner membrane it shuttles electrons between respiratory complexes; in its reduced form (ubiquinol) it is a potent membrane-bound antioxidant. CoQ10 levels decline with age and statin use.

Mechanism of Action

Coenzyme Q10 (ubiquinone/ubiquinol) is a lipophilic quinone molecule in the mitochondrial respiratory chain that transfers electrons from Complexes I and II to Complex III. The Q-cycle between its fully oxidized and fully reduced forms sustains the proton gradient to feed ATP synthase. The reduced form ubiquinol is an antioxidant that breaks membrane lipid peroxidation.

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Glutathione (GSH) is a tripeptide with a γ-glutamyl-cysteine-glycine structure. Via its thiol group it forms conjugates with electrophilic compounds for detoxification; as a cofactor for glutathione peroxidases it reduces H₂O₂ and lipid peroxides. The GSH/GSSG ratio is the primary indicator of cellular redox status.

Mechanism of Action

Glutathione (GSH) is a tripeptide with a γ-glutamyl-cysteine-glycine structure. Via its thiol (-SH) group it forms conjugates with electrophilic compounds for detoxification; as a cofactor for glutathione peroxidases it reduces H₂O₂ and lipid peroxides. The oxidized GSSG form is recycled by glutathione reductase; the GSH/GSSG ratio is the primary indicator of cellular redox status.

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Alpha-lipoic acid (ALA) is a natural cofactor for mitochondrial dehydrogenase complexes and a unique antioxidant. The ALA/DHLA redox couple scavenges reactive oxygen species, regenerates vitamins E and C, and restores glutathione; its solubility in both fat and water earns it the title of 'universal antioxidant.'

Mechanism of Action

Alpha-lipoic acid (ALA) is a natural cofactor for mitochondrial pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase complexes. The ALA/DHLA redox couple scavenges reactive oxygen species including superoxide, hydroxyl, and singlet oxygen, chelates metal ions, and regenerates vitamin E, vitamin C, and glutathione. Its efficacy in both lipophilic and hydrophilic environments earns it recognition as the 'universal antioxidant.'

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Resveratrol is a stilbene-class polyphenolic compound synthesized in grape skins and other plants. It mimics caloric restriction through SIRT1 activation, modulates NF-κB and AMPK pathways for anti-inflammatory effects, and stimulates mitochondrial biogenesis.

Mechanism of Action

Resveratrol is a stilbene-class polyphenolic compound synthesized in grape skins and other plants. It activates SIRT1 to enhance NAD+-dependent deacetylase activity—described as a mimic of caloric restriction. It additionally modulates NF-κB and AMPK pathways for anti-inflammatory effects and stimulates mitochondrial biogenesis.

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Astaxanthin is a unique carotenoid with hydroxyl and keto groups at both ends. Its membrane-spanning structure quenches singlet oxygen within the lipid bilayer and upregulates intrinsic antioxidant defense genes through Nrf2 activation.

Mechanism of Action

Astaxanthin is a unique carotenoid with hydroxyl and keto groups at both ends. Its membrane-spanning structure quenches singlet oxygen and breaks peroxyl chain reactions within the lipid bilayer, providing antioxidant potency many times that of alpha-tocopherol. It also activates the Nrf2 transcription factor, upregulating the cell's intrinsic antioxidant defense genes.

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NMN (nicotinamide mononucleotide) is a critical intermediate in the salvage pathway of NAD+ biosynthesis. After cellular uptake it is converted to NAD+ by NMNAT enzymes, replenishing age-declined NAD+ levels and supporting sirtuin and PARP activity.

Mechanism of Action

NMN (nicotinamide mononucleotide) is a critical intermediate in the salvage pathway of NAD+ biosynthesis. After cellular uptake via transporter proteins, it is converted to NAD+ by NMNAT enzymes. Supplemented NMN replenishes NAD+ levels that decline with aging, supporting sirtuin and PARP activity to maintain metabolic function and mitochondrial biogenesis.

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