Multiple alcohol dehydrogenases but no functional acetaldehyde dehydrogenase causing excessive acetaldehyde production from ethanol by oral streptococci.
Multiple alcohol dehydrogenases but no functional acetaldehyde dehydrogenase causing excessive acetaldehyde production from ethanol by oral streptococci.
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DOI：
10.1099/mic.0.066258-0
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发表时间：
2013-07
期刊：
影响因子：
1.5
通讯作者：
S. Pavlova;Ling Jin;Stephen R Gasparovich;L. Tao
中科院分区：
文献类型：
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作者：
S. Pavlova;Ling Jin;Stephen R Gasparovich;L. Tao
酒精消费和口腔卫生不良是口腔癌和食管癌的危险因素。虽然已发现口腔链球菌从乙醇中产生过量乙醛，但对这种致癌物质产生的机制知之甚少。通过筛选52株不同的口腔链球菌，我们确定了戈登链球菌V2016，从乙醇中产生的乙醛最多。然后，我们在该菌株中构建了基因缺失突变体，并通过酶谱分析了它们的乙醇和乙醛脱氢酶。结果表明，S. gordonii V2016表达三种伯醇脱氢酶AdhA、AdhB和AdhE，它们都将乙醇氧化成乙醛，但它们的优选底物分别是1-丙醇、1-丁醇和乙醇。另外两种脱氢酶，S-AdhA和TdhA，分别被鉴定为对仲醇2-丙醇和苏氨酸具有特异性，但对乙醇没有特异性。S.尽管gordonii V2016的adhE基因编码假定的双功能乙醛/乙醇脱氢酶，但它没有显示出可检测到的乙醛脱氢酶。与野生型和缺失adhA或adhB的突变体相比，缺失adhE的突变体表现出更大的乙醇耐受性，表明AdhE是S. gordonii。对19株S. gordonii，S. mitis，S. oralis，S. salivarius和S. sanguinis显示出多达三种醇脱氢酶的表达，但除了一种显示出新型ALDH的菌株外，没有一种显示出可检测到的乙醛脱氢酶。因此，多种乙醇脱氢酶的表达，但没有功能性乙醛脱氢酶可能有助于某些口腔链球菌从乙醇中过量生产乙醛。
Ethanol consumption and poor oral hygiene are risk factors for oral and oesophageal cancers. Although oral streptococci have been found to produce excessive acetaldehyde from ethanol, little is known about the mechanism by which this carcinogen is produced. By screening 52 strains of diverse oral streptococcal species, we identified Streptococcus gordonii V2016 that produced the most acetaldehyde from ethanol. We then constructed gene deletion mutants in this strain and analysed them for alcohol and acetaldehyde dehydrogenases by zymograms. The results showed that S. gordonii V2016 expressed three primary alcohol dehydrogenases, AdhA, AdhB and AdhE, which all oxidize ethanol to acetaldehyde, but their preferred substrates were 1-propanol, 1-butanol and ethanol, respectively. Two additional dehydrogenases, S-AdhA and TdhA, were identified with specificities to the secondary alcohol 2-propanol and threonine, respectively, but not to ethanol. S. gordonii V2016 did not show a detectable acetaldehyde dehydrogenase even though its adhE gene encodes a putative bifunctional acetaldehyde/alcohol dehydrogenase. Mutants with adhE deletion showed greater tolerance to ethanol in comparison with the wild-type and mutant with adhA or adhB deletion, indicating that AdhE is the major alcohol dehydrogenase in S. gordonii. Analysis of 19 additional strains of S. gordonii, S. mitis, S. oralis, S. salivarius and S. sanguinis showed expressions of up to three alcohol dehydrogenases, but none showed detectable acetaldehyde dehydrogenase, except one strain that showed a novel ALDH. Therefore, expression of multiple alcohol dehydrogenases but no functional acetaldehyde dehydrogenase may contribute to excessive production of acetaldehyde from ethanol by certain oral streptococci.