Nester E W
J Bacteriol. 1968 Nov;96(5):1649-57. doi: 10.1128/jb.96.5.1649-1657.1968.
l-Histidine and, to a lesser degree, l-phenylalanine at concentrations of 10(-4)m inhibit the growth of leaky mutants (bradytrophs) of Bacillus subtilis that are deficient in the synthesis of p-hydroxyphenylpyruvate, the first intermediate specific to tyrosine synthesis. The inhibition can be overcome by growth factor amounts of l-tyrosine and p-hydroxyphenylpyruvate. Histidine and phenylalanine are capable of inhibiting the synthesis of tyrosine in several ways, and the major physiological effect which results in growth inhibition has not been established. Both l-histidine and l-phenylalanine inhibit the activity of prephenate dehydrogenase at concentrations about 100-fold higher than the inhibitory concentration of l-tyrosine. Histidine also appears to repress the synthesis of prephenate dehydrogenase because a histidine bradytroph growing in histidine-supplemented medium has a twofold lower level of this enzyme than the same cells growing in unsupplemented medium. These same two amino acids also inhibit the growth of a bradytroph deficient in dehydroquinate synthetase, an early enzyme in the pathway of tyrosine, phenylalanine, and tryptophan synthesis. The inhibition is overcome by a combination of tyrosine and phenylalanine. Histidine-resistant derivatives of both the prephenate dehydrogenase and dehydroquinate synthetase-deficient strains, which simultaneously have gained resistance to phenylalanine, have been isolated. Most of these resistant mutants synthesize additional tyrosine compared with the parent strain. One class of resistant mutants excretes tyrosine and has a number of enzymes of aromatic acid synthesis which are no longer repressible by any combination of the aromatic amino acids. Tyrosine inhibits the growth of histidine bradytrophs. Histidine, at growth factor levels, overcomes the inhibition.
浓度为10⁻⁴m的L-组氨酸以及浓度稍低的L-苯丙氨酸可抑制枯草芽孢杆菌渗漏突变体（生长缓慢型菌株）的生长，这些突变体在对羟基苯丙酮酸（酪氨酸合成的首个特定中间产物）的合成上存在缺陷。L-酪氨酸和对羟基苯丙酮酸的生长因子量可克服这种抑制作用。组氨酸和苯丙氨酸能够通过多种方式抑制酪氨酸的合成，而导致生长抑制的主要生理效应尚未明确。L-组氨酸和L-苯丙氨酸抑制预苯酸脱氢酶活性的浓度比L-酪氨酸的抑制浓度高约100倍。组氨酸似乎还会抑制预苯酸脱氢酶的合成，因为在添加组氨酸的培养基中生长的组氨酸生长缓慢型菌株中，这种酶的水平比在未添加组氨酸的培养基中生长的相同细胞低两倍。这两种氨基酸还会抑制脱氢奎尼酸合成酶缺陷的生长缓慢型菌株的生长，脱氢奎尼酸合成酶是酪氨酸、苯丙氨酸和色氨酸合成途径中的一种早期酶。酪氨酸和苯丙氨酸的组合可克服这种抑制作用。已分离出预苯酸脱氢酶和脱氢奎尼酸合成酶缺陷菌株的组氨酸抗性衍生物，它们同时也获得了对苯丙氨酸的抗性。与亲本菌株相比，这些抗性突变体中的大多数会合成额外的酪氨酸。一类抗性突变体分泌酪氨酸，并且具有多种芳香酸合成酶，这些酶不再受芳香族氨基酸的任何组合抑制。酪氨酸会抑制组氨酸生长缓慢型菌株的生长。生长因子水平的组氨酸可克服这种抑制作用。
