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首页> 外文期刊>Journal of bacteriology >Obligatory biosynthesis of L-tyrosine via the pretyrosine branchlet in coryneform bacteria.
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Obligatory biosynthesis of L-tyrosine via the pretyrosine branchlet in coryneform bacteria.

机译：通过棒状细菌的预防酪氨酸谱系于L-酪氨酸的强制性生物合成。

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摘要

Species of coryneform bacteria (Corynebacterium glutamicum, Brevibacterium flavum, and B. ammoniagenes) utilize pretyrosine [beta-(1-carboxy-4-hydroxy-2,5-cyclohexadien-1-yl) alanine] as an intermediate in L-tyrosine biosynthesis. Pretyrosine is formed from prephenate via the activity of at least one species of aromatic aminotransferase which is significantly greater with prephenate as substrate than with either phenylpyruvate or 4-hydroxyphenylpyruvate. Pretyrosine dehydrogenase, capable of converting pretyrosine to L-tyrosine, has been partially purified from all three species. Each of the three pretyrosine dehydrogenases is catalytically active with either nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate as cofactors. The Km values for nicotinamide adenine dinucleotide phosphate in C. glutamicum and B. flavum are 55 microM and 14.2 microM, respectively, and corresponding Km values for nicotinamide adenine dinucleotide are 350 microM and 625 microM, respectively. The molecular weights of pretyrosine dehydrogenase in C. glutamicum and in B. flavum are both about 158,000, compared with 68,000 moleculr weitht in B. ammoniagenes. In all three species the enzyme is not feedback inhibited by L-tyrosine. Results obtained with various auxotropic mutants, which were used to manipulate internal concentrations of L-tyrosine, suggest that pretyrosine dehydrogenase is expressed constitutively. Pretyrosine dehydrogenase is quite sensitive to p-hydroxymercuribenzoic acid, complete inhibition being achieved at 10 to 25 microM concentrations. This inhibition is readily reversed by thiol reagents such as 2-mercaptoethanol. Coryneform organisms, like species of blue-green bacteria, appear to lack the 4-hydroxyphenylpyruvate pa thway of L-tyrosine synthesis altogether. The loss of pretyrosine dehydrogenase in extracts prepared from a tyrosine auxotroph affirms the exclusive role of pretyrosine dehydrogenase in L-tyrosine biosynthesis. Other reports in the literature, in which the presence in these organisms of prephenate dehydrogenase is described, appear to be erroneous.
机译：糖胺细菌（谷氨酸棒杆菌，Brevibacterium Blavum和B.Ammoniaes）的种类利用了预称β-（1-羧基-4-羟基-2,5-环己二烯-1-基）丙氨酸作为L-酪氨酸生物合成中的中间体。通过至少一种种类的芳族氨基转移酶的活性由哌妥形成，所述芳族氨基转移酶的活性与哌妥酸盐显着较大，与苯吡合他分或4-羟基苯基吡合他水相比显着更大。能够将预键虫转化为L-酪氨酸的预氢脱氢酶已从所有三种物种中部分纯化。三种预氰酰胺酶中的每一个都与烟酰胺腺嘌呤二核苷酸或烟酰胺腺嘌呤二核苷酸磷酸酯作为辅助粘液催化活性。烟酰胺腺嘌呤二核苷酸磷酸的km值分别为55微米和14.2微米，烟酰胺腺嘌呤二核苷酸的相应km值分别为350微米和625微米。与B.氨中的68,000分子卫生相比，C.谷氨酰胺和B.Flavum在C.谷氨酰胺和B.Flavum的分子量约为158,000。在所有三种物种中，酶不受L-酪氨酸抑制的反馈。用各种助体型突变体获得的结果，用于操纵L-酪氨酸的内部浓度，表明预yrosine脱氢酶组成型表达。预见的脱氢酶对对羟胞嘧啶的苯甲酸非常敏感，在10至25微米浓度下实现完全抑制。通过硫醇试剂如2-巯基乙醇，该抑制性容易逆转。像蓝绿色细菌的种类一样的植物织物生物似乎完全缺乏L-酪氨酸合成的4-羟基苯吡喃吡合他样PA离线。从酪氨酸毒素制备的提取物中丧失的预键素脱氢酶否定了预防酪氨酸脱氢酶在L-酪氨酸生物合成中的专用作用。文献中的其他报道，其中描述了在这些哌妥脱氢酶的这些生物中存在，看起来是错误的。

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