Molecular characteristics and transcription of the gene encoding a multifunctional alcohol dehydrogenase in relation to the deactivation of pyruvate formate-lyase in the ruminal bacterium Streptococcus bovis
Molecular characteristics and transcription of the gene encoding a multifunctional alcohol dehydrogenase in relation to the deactivation of pyruvate formate-lyase in the ruminal bacterium Streptococcus bovis
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DOI：
10.1007/s00203-003-0638-0
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发表时间：
2004-02-01
影响因子：
2.8
通讯作者：
Hino, T
中科院分区：
文献类型：
--
作者：
Asanuma, N;Yoshii, T;Hino, T
为阐明丙酮酸甲酸裂解酶（PFL）的失活机制及其在牛链球菌发酵调控中的作用，研究了多功能醇脱氢酶（ADHE）的分子特性和基因表达。S.牛ADHE由872个氨基酸组成，分子量为97.4kDa。ADHE显示具有三种酶活性：（1）醇脱氢酶，（2）催化乙酰辅酶A转化为乙醇的辅酶A连接的乙醛脱氢酶，和（3）PFL失活酶。与大肠杆菌ADHE、S.牛ADHE的活性需要Fe ~（2+）。编码ADHE（adhE）的基因显示为单顺反子。随着生长条件的改变，adhE mRNA的水平与编码PFL（pfl）和PFL激活酶（act）的基因的mRNA水平平行变化，尽管这些基因独立转录。ADHE、PFL激活酶和PFL的合成似乎同时受到调节。ADHE的过表达没有引起甲酸-乳酸比的变化。可以想象，在缺氧条件下，ADHE不显著参与活性PFL的可逆失活。从丙酮酸流量的分配似乎主要是由乳酸脱氢酶和PFL的活动调节。
To clarify the deactivation mechanism of pyruvate formate-lyase (PFL) and its role in the regulation of fermentation in Streptococcus bovis, the molecular properties and genetic expression of multifunctional alcohol dehydrogenase (ADHE) were investigated. S. bovis was found to have ADHE, which was deduced to consist of 872 amino acids with a molecular mass of 97.4 kDa. The ADHE was shown to harbor three enzyme activities: (1) alcohol dehydrogenase, (2) coenzyme-A-linked acetaldehyde dehydrogenase that catalyzes the conversion of acetyl-CoA to ethanol, and (3) PFL deactivase. Similar to Escherichia coli ADHE, S. bovis ADHE required Fe2+ for its activity. The gene encoding ADHE (adhE) was shown to be monocistronic. The level of adhE mRNA changed in parallel with the mRNA levels of the genes encoding PFL (pfl) and PFL-activating enzyme (act) as the growth conditions changed, although these genes are independently transcribed. Synthesis of ADHE, PFL-activating enzyme, and PFL appears to be regulated concomitantly. Overexpression of ADHE did not cause a change in the formate-to-lactate ratio. It is conceivable that ADHE is not significantly involved in the reversible inactivation of active PFL under anoxic conditions. Partition of the flow from pyruvate appears to be mainly regulated by the activities of lactate dehydrogenase and PFL.