ISOCHORISMATE HYDROXYMUTASE FROM A CELL-SUSPENSION CULTURE OF GALIUM-MOLLUGO L

Isochorismate hydroxymutase (i.e. isochorismate synthase, EC 5,4.99.6) was purified from an anthraquinone-producing cell-suspension culture of Galium mollugo L, Although attempts to stabilize the labile enzyme met with little success, a substantial increase in enzyme activity was observed in the presence of glycine betaine (500 mM). Column chromato graphy on solid supports other than diethylaminoethyl (DEAE)- Sephacel , Phenylsepharose Cl-4B or Cibacron Blue 3G-A did not give active enzy me preparations. In spite of these drawbacks the enzyme was purified 5 73-fold. Enzyme activity depended strictly on the presence of Mg2+ Kin etic data for chorismate in the forward reaction (K-m = 807 mu M, V-ma x = 6.2 pkat.mg(-1)) and for isochorismate in the reverse reaction (K- m = 675 mu MVmax = 5.9 pkat.mg(-1)) were determined.