Literature summary extracted from

Macaulay, K.M.; Heath, G.A.; Ciulli, A.; Murphy, A.M.; Abell, C.; Carr, J.P.; Smith, A.G.
The biochemical properties of the two Arabidopsis thaliana isochorismate synthases (2017), Biochem. J., 474, 1579-1590 .

Cloned(Commentary)

EC Number	Cloned (Comment)	Organism
5.4.4.2	gene ICS1, located on chromosome 1, cloning from seedling cDNA library, recombinant expression of His6-tagged isozyme ICS1 in Escherichia coli strain Rosetta DE3 pLysS	Arabidopsis thaliana
5.4.4.2	gene ICS2, located on chromosome 1, cloning from pFL61 library, functional recombinant expression of His6-tagged isozyme ICS2 in Escherichia coli strain Rosetta DE3 pLysS	Arabidopsis thaliana

KM Value [mM]

EC Number	KM Value [mM]	KM Value Maximum [mM]	Substrate	Comment	Organism	Structure
5.4.4.2	additional information	-	additional information	Michaelis-Menten kinetics	Arabidopsis thaliana
5.4.4.2	0.0288	-	chorismate	isozyme ICS1, pH 7.0, 33°C	Arabidopsis thaliana
5.4.4.2	0.0343	-	chorismate	isozyme ICS1, pH 7.0, 33°C	Arabidopsis thaliana

Localization

EC Number	Localization	Comment	Organism	GeneOntology No.	Textmining
5.4.4.2	chloroplast	-	Arabidopsis thaliana	9507	-

Metals/Ions

EC Number	Metals/Ions	Comment	Organism	Structure
5.4.4.2	Mg2+	dependent on, Km for ICS1 is 0.942 mM	Arabidopsis thaliana
5.4.4.2	Mg2+	dependent on, Km for ICS2 is 0.55 mM	Arabidopsis thaliana

Natural Substrates/ Products (Substrates)

EC Number	Natural Substrates	Organism	Comment (Nat. Sub.)	Natural Products	Comment (Nat. Pro.)	Rev.	Reac.
5.4.4.2	Chorismate	Arabidopsis thaliana	-	Isochorismate	-	r

Organism

EC Number	Organism	UniProt	Comment	Textmining
5.4.4.2	Arabidopsis thaliana	Q9M9V6	-	-
5.4.4.2	Arabidopsis thaliana	Q9S7H8	-	-

Purification (Commentary)

EC Number	Purification (Comment)	Organism
5.4.4.2	recombinant His6-tagged isozyme ICS1 from Escherichia coli strain Rosetta DE3 pLysS by nickel affinity chromatography and gel filtration	Arabidopsis thaliana
5.4.4.2	recombinant His6-tagged isozyme ICS2 from Escherichia coli strain Rosetta DE3 pLysS by nickel affinity chromatography and gel filtration	Arabidopsis thaliana

Source Tissue

EC Number	Source Tissue	Comment	Organism	Textmining
5.4.4.2	hydathode	-	Arabidopsis thaliana	-
5.4.4.2	leaf	-	Arabidopsis thaliana	-
5.4.4.2	plant vascular cell	isozyme AtICS2 appears to be expressed constitutively, predominantly in the plant vasculature. AtICS2 expression in leaf tissue appears to be localized most strongly in the vasculature and hydathodes	Arabidopsis thaliana	-

Substrates and Products (Substrate)

EC Number	Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
5.4.4.2	Chorismate	-	Arabidopsis thaliana	Isochorismate	-	r
5.4.4.2	additional information	isozyme ICS1 does not act as isochorismate pyruvate lyase (IPL, EC 4.2.99.21) and bifunctional salicylate synthase, it does not convert chorismate into salicylate	Arabidopsis thaliana	?	-	?
5.4.4.2	additional information	isozyme ICS2 does not act as isochorismate pyruvate lyase (IPL, EC 4.2.99.21) and bifunctional salicylate synthase, it does not convert chorismate into salicylate	Arabidopsis thaliana	?	-	?

Subunits

EC Number	Subunits	Comment	Organism
5.4.4.2	?	x * 60000, about, recombinant His6-tagged isozyme ICS1, SDS-PAGE	Arabidopsis thaliana
5.4.4.2	?	x * 60000, about, recombinant His6-tagged isozyme ICS2, SDS-PAGE	Arabidopsis thaliana
5.4.4.2	More	isozyme ICS1 structure comparisons with isozyme ICS2 and other enzymes, overview	Arabidopsis thaliana
5.4.4.2	More	isozyme ICS2 structure comparisons with isozyme ICS1 and other enzymes, overview	Arabidopsis thaliana

Synonyms

EC Number	Synonyms	Comment	Organism
5.4.4.2	AtICS1	-	Arabidopsis thaliana
5.4.4.2	AtICS2	-	Arabidopsis thaliana
5.4.4.2	ICS1	-	Arabidopsis thaliana
5.4.4.2	ICS2	-	Arabidopsis thaliana
5.4.4.2	isochorismate hydroxymutase	-	Arabidopsis thaliana
5.4.4.2	isochorismate mutase 1	-	Arabidopsis thaliana
5.4.4.2	isochorismate mutase 2	-	Arabidopsis thaliana
5.4.4.2	isochorismate synthase 1, chloroplastic	UniProt name	Arabidopsis thaliana
5.4.4.2	isochorismate synthase 2, chloroplastic	UniProt name	Arabidopsis thaliana

Temperature Optimum [°C]

EC Number	Temperature Optimum [°C]	Temperature Optimum Maximum [°C]	Comment	Organism
5.4.4.2	33	-	-	Arabidopsis thaliana

Temperature Range [°C]

EC Number	Temperature Minimum [°C]	Temperature Maximum [°C]	Comment	Organism
5.4.4.2	additional information	-	isozymes ICS1 and ICS2 activities display a response to temperature that is more typical of most enzymes, with an approximate doubling in reaction rate per 10°C between 10 and about 33°C, while at temperatures higher than this, reaction rates decline	Arabidopsis thaliana

Turnover Number [1/s]

EC Number	Turnover Number Minimum [1/s]	Turnover Number Maximum [1/s]	Substrate	Comment	Organism	Structure
5.4.4.2	17	-	chorismate	isozyme ICS1, pH 7.0, 33°C	Arabidopsis thaliana
5.4.4.2	38.1	-	chorismate	isozyme ICS1, pH 7.0, 33°C	Arabidopsis thaliana

pH Optimum

EC Number	pH Optimum Minimum	pH Optimum Maximum	Comment	Organism
5.4.4.2	7.5	-	-	Arabidopsis thaliana
5.4.4.2	8	-	-	Arabidopsis thaliana

Expression

EC Number	Organism	Comment	Expression
5.4.4.2	Arabidopsis thaliana	isozyme ICS2 expression is not induced by salicylate, the AtICS2 promoter activity is not stimulated by virus infection	additional information
5.4.4.2	Arabidopsis thaliana	isozyme ICS1 expression is induced throughout the leaf by exogenous salicylate and virus infection. i.e. cucumber mosaic virus but not with tobacco mosaic virus	up

General Information

EC Number	General Information	Comment	Organism
5.4.4.2	evolution	genes ATICS1 and AtICS2 are both located on chromosome 1 on different sides of the centromere, and they are likely a result of a duplication event, since they are bordered by similar genes. At the DNA sequence level, the protein-coding regions of the two genes share a high degree of similarity, but this does not extend into the untranslated regions	Arabidopsis thaliana
5.4.4.2	metabolism	enzyme ICS does not act as isochorismate pyruvate lyase (IPL, EC 4.2.99.21) and bifunctional salicylate synthase, it does not convert chorismate into salicylate. In Arabidopsis thaliana, salicylate is synthesized from chorismic acid, derived from the shikimic acid pathway, occuring in the plastid	Arabidopsis thaliana
5.4.4.2	additional information	homology modeling of isozymes ICS1 and ICS2 using Serratia marcescens anthranilate synthase (TrpE, PDB ID 1I7Q) as reference structure	Arabidopsis thaliana
5.4.4.2	physiological function	isozyme AtICS1 is required for increased salicylate biosynthesis in response to pathogens, and its expression can be stimulated throughout the leaf by virus infection and exogenous salicylate. Isozymes AtICS1 and AtICS2 can be successful in competing for chorismate in vivo	Arabidopsis thaliana
5.4.4.2	physiological function	isozymes AtICS1 and AtICS2 can be successful in competing for chorismate in vivo	Arabidopsis thaliana

kcat/KM [mM/s]

EC Number	kcat/KM Value [1/mMs^-1]	kcat/KM Value Maximum [1/mMs^-1]	Substrate	Comment	Organism	Structure
5.4.4.2	590.3	-	chorismate	isozyme ICS2, pH 7.0, 33°C	Arabidopsis thaliana
5.4.4.2	1110.8	-	chorismate	isozyme ICS1, pH 7.0, 33°C	Arabidopsis thaliana

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Release 2023.1 (January 2023)