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Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
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MetaCyc Enzyme: epithiospecifier protein

Gene: ESP Accession Number: G-9481 (MetaCyc)

Species: Arabidopsis thaliana ler

Summary:
An epithiospecifier protein (ESP) from Arabidopsis thaliana ler has been purified after heterologous expression in Escherichia coli [Burow06]. Since the substrates of ESP, thiohydroximate-O-sulphonates, are unstable, the activity of ESP was assayed with glucosinolates in the presence of myrosinase. The Arabidopsis ESP catalyzes the conversion of alkenylglucosinolates to epithionitriles, whereas nonalkenylglucosinolates were converted to simple nitriles. Aromatic benzylglucosinolates were not substrates of ESP.

The Arabidopsis ESP is completely inactive in citrate and phosphate buffers. The highest activity was found in Mes buffer at pH 6.0. Both Fe2+ and Fe3+ are co-factors that promote ESP activity. The optimum concentration of Fe2+ is 0.5 mM. Chelators of Fe2+ or Fe3+, such as bathophenanthroline disulfonic acid and deferoxamine, strongly inhibit ESP activity. ESP activity is completely blocked by addition of 2 mM EDTA. On the other hand, the enzyme activity is increased by addition of dithiothreitol or beta-mercaptoethanol.

It was also observed that without ESP, myrosinase and Fe2+ are sufficient to convert glucosinolates to simple nitriles.

Molecular Weight of Polypeptide: 37.0 kD (from nucleotide sequence)

Relationship Links: Entrez-Nucleotide:PART-OF:AF416787

Gene-Reaction Schematic: ?


Enzymatic reaction of: thiohydroximate-O-sulfate sulfohydrolase (nitrile-forming) (epithiospecifier protein)

a thiohydroximate-O-sulfate without a terminal alkene <=> a nitrile + sulfate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: glucosinolate breakdown

Cofactors or Prosthetic Groups: Fe3+ [Burow06], Fe2+ [Burow06]

Activators (Unknown Mechanism): dithiothreitol [Burow06] , 2-mercaptoethanol [Burow06]

Inhibitors (Other): EDTA [Burow06] , bathophenanthroline disulfomic acid [Burow06] , desferrioxamine B [Burow06]

Inhibitors (Unknown Mechanism): phosphate [Burow06]

pH(opt): 6.0 [Burow06]


Enzymatic reaction of: alkenyl thiohydroximate-O-sulfate sulfohydrolase (epithionitrile-forming) (epithiospecifier protein)

a thiohydroximate-O-sulfate with a terminal alkene <=> an epithionitrile + sulfate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: glucosinolate breakdown

Summary:

Cofactors or Prosthetic Groups: Fe3+ [Burow06], Fe2+ [Burow06]

Activators (Unknown Mechanism): dithiothreitol [Burow06] , 2-mercaptoethanol [Burow06]

Inhibitors (Other): bathophenanthroline disulfonic acid [Burow06] , desferrioxamine B [Burow06] , EDTA [Burow06]

Inhibitors (Unknown Mechanism): phosphate [Burow06]

pH(opt): 6.0 [Burow06]


References

Burow06: Burow M, Markert J, Gershenzon J, Wittstock U (2006). "Comparative biochemical characterization of nitrile-forming proteins from plants and insects that alter myrosinase-catalysed hydrolysis of glucosinolates." FEBS J 273(11);2432-46. PMID: 16704417


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Wed Nov 26, 2014, biocyc11.