Isochorismate synthase

Isochorismate synthase ( EC 5.4.4.2) is an isomerase enzyme that catalyzes the first step in the biosynthesis of vitamin K₂ (menaquinone) in Escherichia coli.^[1]

Isochorismate synthase
Ishochorismate Synthase cartoon view (2 subunits)
Identifiers
EC no.	5.4.4.2
CAS no.	37318-53-9
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Search PMC articles PubMed articles NCBI proteins

Reaction

Isochorismate synthase, belongs to the isomerase enzyme family. More specifically it is classified as an intramolecular transferase because it transfers the hydroxy group of chorismate between carbons.^[2]

Isochorismate synthase catalyzes the irreversible conversion of chorismate to isochorismate:

Isochorismate synthase is most active at 37 °C and at a pH between 7.5 and 8. It requires Mg²⁺ as a cofactor, in a concentration between 100 μM and 1 mM.^[1] Inhibitors of isochorismate synthase include:

• (4R,5R)-4-hydroxy-5-(1-carboxyvinyloxy)-cyclohex-1-ene carboxylate
• (4R,5R)-4-hydroxy-5-carboxymethoxy-cyclohex-1-enecarboxylate
• (4R,5R)-5-(2-carboxy-allyloxy)-4-hydroxy-cyclohex-1-enecarboxylate
• (4R,5R,6S)-6-ammonio-5-[(1-carboxylatoethenyl)oxy]-4-hydroxycyclohex-1-ene-1-carboxylate
• (4R,5R,7R)-5-(1-carboxy-ethoxy)-4-hydroxy-cyclohex-1-enecarboxylate
• (4R,5R,7S)-5-(1-carboxy-ethoxy)-4-hydroxy-cyclohex-1-enecarboxylate
• (4R,5S,6S)-4-ammonio-5-[(1-carboxylatoethenyl)oxy]-6-hydroxycyclohex-1-ene-1-carboxylate
• (4R,5S,6S)-5-[(1-carboxylatoethenyl)oxy]-4,6-dihydroxycyclohex-1-ene-1-carboxylate^[3]
• Cu²⁺
• Hg²⁺
• K⁺
• Mg²⁺ at concentrations above 1 mM
• N-ethylmaleimide

Nomenclature

The systematic name of this enzyme is isochorismate hydroxymutase, and the common name is isochorismate synthase. Other names for this enzyme include:

• Isochorismate mutase
• Menaquinone-specific isochorismate synthase
• MenF

Pathways

Isochorismate synthase EntC, monomer, E.Coli

MenF is a gene that codes for the isochorismate synthase found in the menaquinone pathway in Escherichia coli, not to be mistaken for the entC gene that codes for the isochorismate synthase found in the enterobactin pathway in Escherichia coli.^[1] This enzyme catalyzes the first step in the biosynthesis of salicylic acid in Pseudomonas aeruginosa.^[4] Isochorismate synthase has several other homologs that are found in other organisms. These include:

Enzyme Genes/Enzyme Names	Organisms
ICS	Arabidopsis thaliana Cyanidium caldarium Glycine max Nicotiana benthamiana Populus fremontil Populus angustifolia Populus tremuloides
ICS1	Arabidopsis thaliana
ICS1 gene product	Arabidopsis thaliana Cyanidium caldarium
ICS2	Arabidopsis thaliana
Isochorismate synthase	Arabidopsis thaliana Cyanidium caldarium Glycine max
Isochorismate synthase 1	Arapidopsis thaliana
Mbtl	Mycobacterium tuberculosis
PchA	Pseudomonas aeruginosa