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, chive thiosulfinates, cysteine sulfoxide degradation
|Superclasses:||Degradation/Utilization/Assimilation → Secondary Metabolites Degradation → Nitrogen Containing Secondary Compounds Degradation|
Expected Taxonomic Range: Allioideae
Plants belonging to the Amaryllidaceae subfamilie Allioideae have been valued both for flavor and medicinal purposes throughout the world. Uncrushed whole chive (Allium tuberosum) bulbs contain, in equal amounts, cysteine sulfoxides and γ-glutamylcysteines as the major organosulfur compounds. The odorless nonprotein ethiin is one of the substrates which is acted upon by the allinase enzyme [Van92]. The enzyme and substrate are compartmentalized in the vacuoles and cell cytoplasm, respectively [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 of many species of the Allioideae 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]. Allium tuberosum contains all the different types of allin cysteine sulfoxides [Manabe98].
Allinases require pyridoxal 5'-phosphate as a cofactor; after binding alliin is converted to allylsulfenate [Shimon07], which 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].
Although pathways with partial experimental proof have been proposed the biosynthesis of the flavor precursor ethiin is still not completely understood [Jones04]. Hence, currently only the degradation of ethiin [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
Lancaster00a: Lancaster JE, Shaw ML, Joyce MD, McCallum JA, McManus MT (2000). "A novel alliinase from onion roots. Biochemical characterization and cDNA cloning." Plant Physiol 122(4);1269-79. PMID: 10759524
Selby80: Selby, C, Turnbull, A, Collin, H. A (1980). "Comparison of the onion plant (Allium cepa) and onion tissue culture. II. Stimultaion of flavour precursor synthesis in onion tissue cultures." New Phytol. 84, 307-312.
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