抄録
Azaserine-resistant mutants derived from a 5-fluorotryptophan-resistant, L-tryptophan-producing mutant of Brevibacterium flavum, accumulated 10.3 g/liter of L-tryptophan at maximum. The production increased to 11.4 g/liter when L-serine was added. In the mutant, only anthranilate synthase among enzymes of the tryptophan-specific biosynthetic pathway increased in activity to a 2-fold higher level than that in the parent strain, No. 187. Sensitivity of anthranilate synthase to the feedback inhibition was not altered by the mutation. Activity of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, the first common enzyme for aromatic amino acid biosynthesis, also increased 2.7-fold and was less sensitive to the feedback inhibition by phenylalanine and tyrosine. Tryptophan transport activity in strain A-100 was similar as that in the parent. Azaserine inhibited anthranilate synthase activity by 50% at 0.075 mM. The inhibition was of a mixed type with respect to both the two substrates. Anthranilate synthase of strain A-100 was inhibited in a similar manner to that of the parent.
