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: molybdenum cofactor (sulfide) biosynthesis
|Superclasses:||Biosynthesis → Cofactors, Prosthetic Groups, Electron Carriers Biosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col
The transition element molybdenum (Mo) has been long known as an essential micronutrient across the kingdoms of plants, animals, fungi and bacteria. However, molybdate itself is catalytically inactive and, with the exception of bacterial nitrogenase, needs to be activated through complexation by a special cofactor. This molybdenum cofactor (moco) consists of a unique tricyclic pterin compound (molybdopterin) containing a Mo-binding and -coordinating dithiolene group. Moco finally binds to diverse apoproteins and confers activity to the resulting holoproteins ubiquitously involved in essential redox reactions in the global C-, N-, and S-cycles [Hille96] [Hansch05].
Although molybdenum enzymes are found in all organism kingdoms only four enzymes have been reported in plants so far [Mendel02]. However, the importance of those enzymes is highlighted by the fact that unavailability of Mo, hence failure to complement the apoproteins with moco is lethal for the organism. Moco enzymes in plants are subdivided into two classes, assimilatory nitrate reductase (NADH) [Crawford88] and sulfite oxidase [Eilers01] originating from the dioxo-form of moco and xanthine dehydrogenase [Hesberg04] and aldehyde oxidase / indole-3-acetaldehyde oxidase / abscisic aldehyde oxidase [Seo00a] that require the addition of a terminal inorganic sulfur to the Mo center (sulfo-form of moco) for enzymatic activity.
The chemical nature and biosynthesis of moco has been investigated in detail in bacteria, e.g. [Wuebbens95, Pitterle93, Pitterle93a, Rajagopalan92a, SantamariaArauj04]. The group of R.R. Mendel (TU Braunschweig) has considerably contributed to the corresponding research in plants which results have been summarized in several excellent reviews [Schwarz06, Mendel06, Mendel02, Mendel05a, Mendel97].
About This Pathway
Plant enzymes such as aldehyde oxidase (AO) and xanthine dehydrogenase (XDH) depend on the sulfo-form of molybdenum cofactor (moco). The so called maturation of moco involves the addition of sulfur to the Mo center catalyzed by the moco sulfurase (ABA3) [Bittner01, Heidenreich05]. This enzyme again is a two-domain protein that generates an enzyme-bound persulfide intermediate (ABA3-NifS domain) whereas the C-terminal domain is probably involved in recognizing target enzymes and posttranslational activation of ABA3 [Bittner01]. However, whether the sulfuration of moco is carried out before or after the insertion into the apoenzyme remains to be investigated.
Bittner01: Bittner F, Oreb M, Mendel RR (2001). "ABA3 is a molybdenum cofactor sulfurase required for activation of aldehyde oxidase and xanthine dehydrogenase in Arabidopsis thaliana." J Biol Chem 276(44);40381-4. PMID: 11553608
Crawford88: Crawford NM, Smith M, Bellissimo D, Davis RW (1988). "Sequence and nitrate regulation of the Arabidopsis thaliana mRNA encoding nitrate reductase, a metalloflavoprotein with three functional domains." Proc Natl Acad Sci U S A 1988;85(14);5006-10. PMID: 3393528
Eilers01: Eilers T, Schwarz G, Brinkmann H, Witt C, Richter T, Nieder J, Koch B, Hille R, Hansch R, Mendel RR (2001). "Identification and biochemical characterization of Arabidopsis thaliana sulfite oxidase. A new player in plant sulfur metabolism." J Biol Chem 276(50);46989-94. PMID: 11598126
Heidenreich05: Heidenreich T, Wollers S, Mendel RR, Bittner F (2005). "Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration." J Biol Chem 280(6);4213-8. PMID: 15561708
Hesberg04: Hesberg C, Hansch R, Mendel RR, Bittner F (2004). "Tandem orientation of duplicated xanthine dehydrogenase genes from Arabidopsis thaliana: differential gene expression and enzyme activities." J Biol Chem 279(14);13547-54. PMID: 14726515
Pitterle93: Pitterle DM, Johnson JL, Rajagopalan KV (1993). "In vitro synthesis of molybdopterin from precursor Z using purified converting factor. Role of protein-bound sulfur in formation of the dithiolene." J Biol Chem 268(18);13506-9. PMID: 8514783
Pitterle93a: Pitterle DM, Rajagopalan KV (1993). "The biosynthesis of molybdopterin in Escherichia coli. Purification and characterization of the converting factor." J Biol Chem 268(18);13499-505. PMID: 8514782
SantamariaArauj04: Santamaria-Araujo JA, Fischer B, Otte T, Nimtz M, Mendel RR, Wray V, Schwarz G (2004). "The tetrahydropyranopterin structure of the sulfur-free and metal-free molybdenum cofactor precursor." J Biol Chem 279(16);15994-9. PMID: 14761975
Seo00a: Seo M, Peeters AJ, Koiwai H, Oritani T, Marion-Poll A, Zeevaart JA, Koornneef M, Kamiya Y, Koshiba T (2000). "The Arabidopsis aldehyde oxidase 3 (AAO3) gene product catalyzes the final step in abscisic acid biosynthesis in leaves." Proc Natl Acad Sci U S A 97(23);12908-13. PMID: 11050171
Wuebbens95: Wuebbens MM, Rajagopalan KV (1995). "Investigation of the early steps of molybdopterin biosynthesis in Escherichia coli through the use of in vivo labeling studies." J Biol Chem 270(3);1082-7. PMID: 7836363
Xiong01: Xiong L, Ishitani M, Lee H, Zhu JK (2001). "The Arabidopsis LOS5/ABA3 locus encodes a molybdenum cofactor sulfurase and modulates cold stress- and osmotic stress-responsive gene expression." Plant Cell 13(9);2063-83. PMID: 11549764
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