Isochorismate synthase

Isochorismate synthase is an enzyme that 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[2]
• Cu²⁺
• Hg²⁺
• K⁺
• Mg²⁺ at concentrations above 1 mM
• NEM

Isochorismate synthase, or MenF, 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.[3] 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

Vitamin K contains a quinone ring that participates in redox reactions. These reactions take place in various organisms such as plants, where electrons are transferred during photosynthesis, humans, where electrons are transferred to modify certain types of proteins, and bacteria, where electrons are transferred during anaerobic respiration.[4]

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 enterobacter pathway in Escherichia coli.[1] Isochorismate synthase has several other homologs that are found in other organisms. These include: