Bakri M M, Rich A M, Cannon R D, Holmes A R
Department of Oral Biology and Biomedical Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia.
Mol Oral Microbiol. 2015 Feb;30(1):27-38. doi: 10.1111/omi.12064. Epub 2014 Sep 15.
Alcohol consumption is a risk factor for oral cancer, possibly via its conversion to acetaldehyde, a known carcinogen. The oral commensal yeast Candida albicans may be one of the agents responsible for this conversion intra-orally. The alcohol dehydrogenase (Adh) family of enzymes are involved in acetaldehyde metabolism in yeast but, for C. albicans it is not known which family member is responsible for the conversion of ethanol to acetaldehyde. In this study we determined the expression of mRNAs from three C. albicans Adh genes (CaADH1, CaADH2 and CaCDH3) for cells grown in different culture media at different growth phases by Northern blot analysis and quantitative reverse transcription polymerase chain reaction. CaADH1 was constitutively expressed under all growth conditions but there was differential expression of CaADH2. CaADH3 expression was not detected. To investigate whether CaAdh1p or CaAdh2p can contribute to alcohol catabolism in C. albicans, each gene from the reference strain C. albicans SC5314 was expressed in Saccharomyces cerevisiae. Cell extracts from an CaAdh1p-expressing S. cerevisiae recombinant, but not an CaAdh2p-expressing recombinant, or an empty vector control strain, possessed ethanol-utilizing Adh activity above endogenous S. cerevisiae activity. Furthermore, expression of C. albicans Adh1p in a recombinant S. cerevisiae strain in which the endogenous ScADH2 gene (known to convert ethanol to acetaldehyde in this yeast) had been deleted, conferred an NAD-dependent ethanol-utilizing, and so acetaldehyde-producing, Adh activity. We conclude that CaAdh1p is the enzyme responsible for ethanol use under in vitro growth conditions, and may contribute to the intra-oral production of acetaldehyde.
饮酒是口腔癌的一个风险因素，可能是通过其转化为乙醛（一种已知的致癌物）。口腔共生酵母白色念珠菌可能是口腔内这种转化的介质之一。乙醇脱氢酶（Adh）家族的酶参与酵母中的乙醛代谢，但对于白色念珠菌来说，尚不清楚哪个家族成员负责将乙醇转化为乙醛。在本研究中，我们通过Northern印迹分析和定量逆转录聚合酶链反应，测定了在不同生长阶段于不同培养基中生长的细胞中，来自三个白色念珠菌Adh基因（CaADH1、CaADH2和CaCDH3）的mRNA表达。CaADH1在所有生长条件下均组成性表达，但CaADH2存在差异表达。未检测到CaADH3的表达。为了研究CaAdh1p或CaAdh2p是否能促进白色念珠菌中的酒精分解代谢，将参考菌株白色念珠菌SC5314的每个基因在酿酒酵母中表达。来自表达CaAdh1p的酿酒酵母重组体的细胞提取物，而非表达CaAdh2p的重组体或空载体对照菌株，具有高于酿酒酵母内源性活性的利用乙醇的Adh活性。此外，在一个重组酿酒酵母菌株中表达白色念珠菌Adh1p，其中内源性ScADH2基因（已知在该酵母中可将乙醇转化为乙醛）已被删除，赋予了一种依赖NAD的利用乙醇并因此产生乙醛的Adh活性。我们得出结论，CaAdh1p是体外生长条件下负责利用乙醇的酶，并且可能有助于口腔内乙醛的产生。
