Regulatory Properties of Chorismate Mutase from Corynebacterium glutamicum

Abstract

Regulatory properties of chorismate mutase from Corynebacterium glutamicum were studied using the dialyzed cell-free extract. The enzyme activity was strongly feedback inhibited by L-phenylalanine (90% inhibition at 0.1_??_1mM) and almost completely by a pair of L-tyrosine and L-phenylalanine (each at 0.1_??_1mM). The enzyme from phenylalanine auxotrophs was scarcely inhibited by L-tyrosine alone but the enzyme from a wild-type strain or a tyrosine auxotroph was weakly inhibited by L-tyrosine alone (40_??_50% inhibition, L-tyrosine at 1mM). The enzyme activity was stimulated by L-tryptophan and the inhibition by L-phenylalanine alone or in the simultaneous presence of L-tyrosine was reversed by L-tryptophan. The Km value of the reaction for chorismate was 2.9×10^-3M. Formation of chorismate mutase was repressed by L-phenylalanine. A phenylalanine auxotrophic L-tyrosine producer, C. glutamicum 98-Tx-71, which is resistant to 3-aminotyrosine, p-aminophenylanaine, p-fluorophenylalanine and tyrosine hydroxamate had chorismate mutase derepressed to two-fold level of the parent KY 10233. The enzyme in C. glutamicum seems to have two physiological roles; one is the control of the metabolic flow to L-phenylalanine and L-tyrosine biosynthesis and the other is the balanced partition of chorismate between L-phenylalanine-L-tyrosine biosynthesis and L-tryptophan biosynthesis.