Monoamine oxidase B has a hydrophobic bipartite elongated cavity that (for the "open" conformation) occupies a combined volume close to 700 Å3. hMAO-A has a single cavity that exhibits a rounder shape and is larger in volume than the "substrate cavity" of hMAO-B.
The first cavity of hMAO-B has been termed the entrance cavity (290 Å3), the second substrate cavity or active site cavity (~390 Å3) – between both an isoleucine199 side-chain serves as a gate. Depending on the substrate or bound inhibitor, it can exist in either an open or a closed form, which has been shown to be important in defining the inhibitor specificity of hMAO B. At the end of the substrate cavity is the FAD coenzyme with sites for favorable amine binding about the flavin involving two nearly parallel tyrosyl (398 and 435) residues that form what has been termed an aromatic cage.
MAO-A is involved in the metabolism of tyramine; inhibition, in particular irreversible inhibition of MAO-A can result in a dangerous pressor effect when foods high in tyramine are consumed such as cheeses (informally known as the "cheese effect"). MAO-A is involved in the metabolism of serotonin, noradrenaline and dopamine whereas MAO-B metabolises the dopamine neurotransmitter. MAO-B is an enzyme on the outer mitochondrial membrane and catalyzes the oxidation of arylalkylamine neurotransmitters
Monoamine oxidase A (MAOA) generally metabolizes tyramine, norepinephrine (NE), serotonin (5-HT), and dopamine (DA) (and other less clinically relevant chemicals). In contrast, Monoamine oxidase B (MAOB) mainly metabolizes dopamine (DA) (and other less clinically relevant chemicals). The differences between the substrate selectivity of the two enzymes are utilized clinically when treating specific disorders: Monoamine oxidase A inhibitors have been typically used in the treatment of depression, and monoamine oxidase B inhibitors are typically used in the treatment of Parkinson's disease. Nonspecific (i.e. MAOA/B combined) inhibitors can pose problems when taken concomitantly with tyramine-containing foods such as cheese, because the drug's inhibition of MAOA causes a dangerous elevation of serum tyramine levels, which can lead to hypertensive symptoms. Selective MAOB inhibitors bypass this problem by preferentially inhibiting MAOB, which mostly metabolizes DA. If MAOB is inhibited, then more DA is available for proper neuronal function, especially in Parkinson's Disease.
Transgenic mice that are unable to produce MAO-B are shown to be resistant to a mouse model of Parkinson's disease. They also demonstrate increased responsiveness to stress (as with MAO-A knockout mice) and increased β-PEA. In addition, they exhibit behavioral disinhibition and reduced anxiety-like behaviors.
Inhibition of MAO-B in rats has been shown to prevent many age-related biological changes such as optic nerve degeneration, and extend average lifespan by up to 39%.
^Youdim MB, Weinstock M (January 2004). "Therapeutic applications of selective and non-selective inhibitors of monoamine oxidase A and B that do not cause significant tyramine potentiation". Neurotoxicology. 25 (1–2): 243–50. doi:10.1016/S0161-813X(03)00103-7. PMID14697899.
^Binda C, Hubálek F, Li M, Herzig Y, Sterling J, Edmondson DE, Mattevi A (March 2004). "Crystal structures of monoamine oxidase B in complex with four inhibitors of the N-propargylaminoindan class". J. Med. Chem. 47 (7): 1767–74. doi:10.1021/jm031087c. PMID15027868.
^Nolen WA, Hoencamp E, Bouvy PF, Haffmans PM (1993). "Reversible monoamine oxidase-A inhibitors in resistant major depression". Clin Neuropharmacol. 16 (Suppl 2): S69–76. PMID8313400.
^Nagatsu T, Sawada M (2006). "Molecular mechanism of the relation of monoamine oxidase B and its inhibitors to Parkinson's disease: possible implications of glial cells". J. Neural Transm. Suppl. Journal of Neural Transmission. Supplementa. 71 (71): 53–65. doi:10.1007/978-3-211-33328-0_7. ISBN978-3-211-33327-3. PMID17447416.
^Kumar MJ, Andersen JK (August 2004). "Perspectives on MAO-B in aging and neurological disease: where do we go from here?". Mol. Neurobiol. 30 (1): 77–89. doi:10.1385/MN:30:1:077. PMID15247489.
^Kitani K, Kanai S, Sato Y, Ohta M, Ivy GO, Carrillo MC (1993). "Chronic treatment of (-)deprenyl prolongs the life span of male Fischer 344 rats. Further evidence". Life Sci. 52 (3): 281–8. doi:10.1016/0024-3205(93)90219-S. PMID8423709.
^Miklya I (December 2009). "[Slowing the age-induced decline of brain function with prophylactic use of (−)-deprenyl (Selegiline, Jumex). Current international view and conclusions 25 years after the Knoll's proposal]". Neuropsychopharmacol Hung (in Hungarian). 11 (4): 217–25. PMID20150659.
^Ukraintseva SV, Arbeev KG, Michalsky AI, Yashin AI (June 2004). "Antiaging treatments have been legally prescribed for approximately thirty years". Ann. N. Y. Acad. Sci. 1019: 64–9. doi:10.1196/annals.1297.014. PMID15246996.
^ abcNovaroli L, Daina A, Favre E, Bravo J, Carotti A, Leonetti F, Catto M, Carrupt PA, Reist M (October 2006). "Impact of species-dependent differences on screening, design, and development of MAO B inhibitors". J. Med. Chem. 49 (21): 6264–72. doi:10.1021/jm060441e. PMID17034132.
^Carotti A, Carrieri A, Chimichi S, Boccalini M, Cosimelli B, Gnerre C, Carotti A, Carrupt PA, Testa B (December 2002). "Natural and synthetic geiparvarins are strong and selective MAO-B inhibitors. Synthesis and SAR studies". Bioorg. Med. Chem. Lett. 12 (24): 3551–5. doi:10.1016/S0960-894X(02)00798-9. PMID12443774.
^Uebelhack R, Franke L, Schewe HJ (September 1998). "Inhibition of platelet MAO-B by kava pyrone-enriched extract from Piper methysticum Forster (kava-kava)". Pharmacopsychiatry. 31 (5): 187–92. doi:10.1055/s-2007-979325. PMID9832350.
^Leonetti F, Capaldi C, Pisani L, Nicolotti O, Muncipinto G, Stefanachi A, Cellamare S, Caccia C, Carotti A (October 2007). "Solid-phase synthesis and insights into structure-activity relationships of safinamide analogues as potent and selective inhibitors of type B monoamine oxidase". Journal of Medicinal Chemistry. 50 (20): 4909–16. doi:10.1021/jm070725e. PMID17824599.
^compound #2d, Frédérick R, Dumont W, Ooms F, Aschenbach L, Van der Schyf CJ, Castagnoli N, Wouters J, Krief A (June 2006). "Synthesis, structural reassignment, and biological activity of type B MAO inhibitors based on the 5H-indeno[1,2-c]pyridazin-5-one core". J. Med. Chem. 49 (12): 3743–7. doi:10.1021/jm051091j. PMID16759116.
^Carotti A, Catto M, Leonetti F, Campagna F, Soto-Otero R, Méndez-Alvarez E, Thull U, Testa B, Altomare C (November 2007). "Synthesis and monoamine oxidase inhibitory activity of new pyridazine-, pyrimidine- and 1,2,4-triazine-containing tricyclic derivatives". Journal of Medicinal Chemistry. 50 (22): 5364–71. doi:10.1021/jm070728r. PMID17910428.
^Chimenti F, Fioravanti R, Bolasco A, Chimenti P, Secci D, Rossi F, Yáñez M, Orallo F, Ortuso F, Alcaro S (May 2009). "Chalcones: a valid scaffold for monoamine oxidases inhibitors". J. Med. Chem. 52 (9): 2818–24. doi:10.1021/jm801590u. PMID19378991.
^compound #21, Silvestri R, La Regina G, De Martino G, Artico M, Befani O, Palumbo M, Agostinelli E, Turini P (March 2003). "Simple, potent, and selective pyrrole inhibitors of monoamine oxidase types A and B". J. Med. Chem. 46 (6): 917–20. doi:10.1021/jm0256124. PMID12620068.
^compound # (R)-8b, Chimenti F, Secci D, Bolasco A, Chimenti P, Granese A, Carradori S, Yáñez M, Orallo F, Sanna ML, Gallinella B, Cirilli R (September 2010). "Synthesis, stereochemical separation, and biological evaluation of selective inhibitors of human MAO-B: 1-(4-arylthiazol-2-yl)-2-(3-methylcyclohexylidene)hydrazines". J. Med. Chem. 53 (17): 6516–20. doi:10.1021/jm100120s. PMID20715818.
^compound #18, Chimenti F, Maccioni E, Secci D, Bolasco A, Chimenti P, Granese A, Befani O, Turini P, Alcaro S, Ortuso F, Cardia MC, Distinto S (February 2007). "Selective inhibitory activity against MAO and molecular modeling studies of 2-thiazolylhydrazone derivatives". J. Med. Chem. 50 (4): 707–12. doi:10.1021/jm060869d. PMID17253676.
^compound #3g, Chimenti F, Fioravanti R, Bolasco A, Manna F, Chimenti P, Secci D, Befani O, Turini P, Ortuso F, Alcaro S (February 2007). "Monoamine oxidase isoform-dependent tautomeric influence in the recognition of 3,5-diaryl pyrazole inhibitors". J. Med. Chem. 50 (3): 425–8. doi:10.1021/jm060868l. PMID17266193.
^compound #(S)-1, Chimenti F, Maccioni E, Secci D, Bolasco A, Chimenti P, Granese A, Befani O, Turini P, Alcaro S, Ortuso F, Cirilli R, La Torre F, Cardia MC, Distinto S (November 2005). "Synthesis, molecular modeling studies, and selective inhibitory activity against monoamine oxidase of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)- pyrazole derivatives". J. Med. Chem. 48 (23): 7113–22. doi:10.1021/jm040903t. PMID16279769.
^Mishra N, Sasmal D (April 2011). "Development of selective and reversible pyrazoline based MAO-B inhibitors: virtual screening, synthesis and biological evaluation". Bioorg. Med. Chem. Lett. 21 (7): 1969–73. doi:10.1016/j.bmcl.2011.02.030. PMID21377879.
^compound #41, Catto M, Nicolotti O, Leonetti F, Carotti A, Favia AD, Soto-Otero R, Méndez-Alvarez E, Carotti A (2006). "Structural insights into monoamine oxidase inhibitory potency and selectivity of 7-substituted coumarins from ligand- and target-based approaches". Journal of Medicinal Chemistry. 49 (16): 4912–25. doi:10.1021/jm060183l. PMID16884303.
^compound #2, Matos MJ, Vazquez-Rodriguez S, Uriarte E, Santana L, Viña D (July 2011). "MAO inhibitory activity modulation: 3-Phenylcoumarins versus 3-benzoylcoumarins". Bioorg. Med. Chem. Lett. 21 (14): 4224–7. doi:10.1016/j.bmcl.2011.05.074. PMID21684743.
^Matos MJ, Viña D, Janeiro P, Borges F, Santana L, Uriarte E (September 2010). "New halogenated 3-phenylcoumarins as potent and selective MAO-B inhibitors". Bioorg. Med. Chem. Lett. 20 (17): 5157–60. doi:10.1016/j.bmcl.2010.07.013. PMID20659799.
^Matos MJ, Viña D, Picciau C, Orallo F, Santana L, Uriarte E (September 2009). "Synthesis and evaluation of 6-methyl-3-phenylcoumarins as potent and selective MAO-B inhibitors". Bioorg. Med. Chem. Lett. 19 (17): 5053–5. doi:10.1016/j.bmcl.2009.07.039. PMID19628387.
^Matos MJ, Viña D, Quezada E, Picciau C, Delogu G, Orallo F, Santana L, Uriarte E (June 2009). "A new series of 3-phenylcoumarins as potent and selective MAO-B inhibitors". Bioorg. Med. Chem. Lett. 19 (12): 3268–70. doi:10.1016/j.bmcl.2009.04.085. PMID19423346.
^compound #9, #12, Gaspar A, Reis J, Fonseca A, Milhazes N, Viña D, Uriarte E, Borges F (January 2011). "Chromone 3-phenylcarboxamides as potent and selective MAO-B inhibitors". Bioorg. Med. Chem. Lett. 21 (2): 707–9. doi:10.1016/j.bmcl.2010.11.128. PMID21194943.
^compound #9i, Manley-King CI, Bergh JJ, Petzer JP (January 2011). "Inhibition of monoamine oxidase by selected C5- and C6-substituted isatin analogues". Bioorg. Med. Chem. 19 (1): 261–74. doi:10.1016/j.bmc.2010.11.028. PMID21134756.
^Strydom B, Malan SF, Castagnoli N, Bergh JJ, Petzer JP (February 2010). "Inhibition of monoamine oxidase by 8-benzyloxycaffeine analogues". Bioorg. Med. Chem. 18 (3): 1018–28. doi:10.1016/j.bmc.2009.12.064. PMID20093036.
^Vlok N, Malan SF, Castagnoli N, Bergh JJ, Petzer JP (May 2006). "Inhibition of monoamine oxidase B by analogues of the adenosine A2A receptor antagonist (E)-8-(3-chlorostyryl)caffeine (CSC)". Bioorg. Med. Chem. 14 (10): 3512–21. doi:10.1016/j.bmc.2006.01.011. PMID16442801.
^Pretorius J, Malan SF, Castagnoli N, Bergh JJ, Petzer JP (September 2008). "Dual inhibition of monoamine oxidase B and antagonism of the adenosine A(2A) receptor by (E,E)-8-(4-phenylbutadien-1-yl)caffeine analogues". Bioorganic & Medicinal Chemistry. 16 (18): 8676–84. doi:10.1016/j.bmc.2008.07.088. PMID18723354.
^Tzvetkov; et al. (June 23, 2014). "Indazole- and Indole-5-carboxamides: Selective and Reversible Monoamine Oxidase B Inhibitors with Subnanomolar Potency". Journal of Medicinal Chemistry. 57 (15): 6679–6703. doi:10.1021/jm500729a. PMID24955776.