This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: thiosulfinate biosynthesis, allium thiosulfinates, garlic thiosulfinate, cysteine sulfoxide degradation
|Superclasses:||Degradation/Utilization/Assimilation → Secondary Metabolites Degradation → Nitrogen Containing Secondary Compounds Degradation|
Expected Taxonomic Range: Allioideae
Plants belonging to the Allioideae family have been valued both for flavor and medicinal purposes throughout the world. Uncrushed whole garlic bulbs contain in equal amounts as major organosulfur compounds cysteine sulfoxides and γ-glutamylcysteines . The odorless non protein alliin is the substrate which is acted upon by the allinase enzyme [Van92]. In garlic, the enzyme and substrate are contained within a specific tissue, i.e. the bundle sheath cells of the clove [Ellmore94] and compartmentalized more specifically in the vacuole (alliinase) and cell cytoplasm (alliin) [Shimon07]. The characteristic pungent odor is emitted only when the tissue is crushed and the enzyme interacts with the substrate.
The degradation of allium organosulphur compounds occurs mainly in bulbs and the allinase enzyme has been purified from bulbs as well as leaves and also from a number of other plants including Acacia and Brassicaceae members [Van92]. Allinases are now reported from a wide variety of organisms including bacteria and fungi [Rössner02]. The variety and composition of organosulfur compounds in Allium is explained by the kinetics of cysteine sulfoxide hydrolysis and the reactivity of the initial sulfenic acids [Rose05]. The allinase of Allium sativum accumulates S-alkyl and S-2-propenyl (allyl) derivatives but not S-1-propenyl derivatives [Manabe98].
Allinases require pyridoxal 5'-phosphate as a cofactor. Following the cofactor binding allinase is able to convert alliin to allylsulfenate [Shimon07], which in turn reacts spontaneously to form allicin, a parent compound of a number of other sulfur-containing compounds such as thiosulfinates, allyl sulfides, dithiines and ajoenes [Shimon07]. The biosynthesis of the flavor precursor alliin is still not completely understood [Jones04] although, there are proposed pathways with partial experimental proof. Hence, currently only the degradation of the alliin [Hughes05] is shown here.
Superpathways: superpathway of alliin degradation
Manabe98: Manabe T, Hasumi A, Sugiyama M, Yamazaki M, Saito K (1998). "Alliinase [S-alk(en)yl-L-cysteine sulfoxide lyase] from Allium tuberosum (Chinese chive)--purification, localization, cDNA cloning and heterologous functional expression." Eur J Biochem 257(1);21-30. PMID: 9799098
Rose05: Rose P, Whiteman M, Moore PK, Zhu YZ (2005). "Bioactive S-alk(en)yl cysteine sulfoxide metabolites in the genus Allium: the chemistry of potential therapeutic agents." Nat Prod Rep 22(3);351-68. PMID: 16010345
Shimon07: Shimon LJ, Rabinkov A, Shin I, Miron T, Mirelman D, Wilchek M, Frolow F (2007). "Two structures of alliinase from Alliium sativum L.: apo form and ternary complex with aminoacrylate reaction intermediate covalently bound to the PLP cofactor." J Mol Biol 366(2);611-25. PMID: 17174334
Van92: Van Damme EJ, Smeets K, Torrekens S, Van Leuven F, Peumans WJ (1992). "Isolation and characterization of alliinase cDNA clones from garlic (Allium sativum L.) and related species." Eur J Biochem 209(2);751-7. PMID: 1385120
Nock87: Nock LP, Mazelis M (1987). "The C-S Lyases of Higher Plants : Direct Comparison of the Physical Properties of Homogeneous Alliin Lyase of Garlic (Allium sativum) and Onion (Allium cepa)." Plant Physiol 85(4);1079-83. PMID: 16665807
Rabinkov94: Rabinkov A, Zhu XZ, Grafi G, Galili G, Mirelman D (1994). "Alliin lyase (Alliinase) from garlic (Allium sativum). Biochemical characterization and cDNA cloning." Appl Biochem Biotechnol 48(3);149-71. PMID: 7979352
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