Keshav K F, Yomano L P, An H J, Ingram L O
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611.
J Bacteriol. 1990 May;172(5):2491-7. doi: 10.1128/jb.172.5.2491-2497.1990.
Zymomonas mobilis ferments sugars to produce ethanol with two biochemically distinct isoenzymes of alcohol dehydrogenase. The adhA gene encoding alcohol dehydrogenase I has now been sequenced and compared with the adhB gene, which encodes the second isoenzyme. The deduced amino acid sequences for these gene products exhibited no apparent homology. Alcohol dehydrogenase I contained 337 amino acids, with a subunit molecular weight of 36,096. Based on comparisons of primary amino acid sequences, this enzyme belongs to the family of zinc alcohol dehydrogenases which have been described primarily in eucaryotes. Nearly all of the 22 strictly conserved amino acids in this group were also conserved in Z. mobilis alcohol dehydrogenase I. Alcohol dehydrogenase I is an abundant protein, although adhA lacked many of the features previously reported in four other highly expressed genes from Z. mobilis. Codon usage in adhA is not highly biased and includes many codons which were unused by pdc, adhB, gap, and pgk. The ribosomal binding region of adhA lacked the canonical Shine-Dalgarno sequence found in the other highly expressed genes from Z. mobilis. Although these features may facilitate the expression of high enzyme levels, they do not appear to be essential for the expression of Z. mobilis adhA.
运动发酵单胞菌通过两种生化性质不同的乙醇脱氢酶同工酶将糖发酵产生乙醇。编码乙醇脱氢酶I的adhA基因现已测序，并与编码第二种同工酶的adhB基因进行了比较。这些基因产物的推导氨基酸序列没有明显的同源性。乙醇脱氢酶I含有337个氨基酸，亚基分子量为36,096。基于一级氨基酸序列的比较，该酶属于主要在真核生物中描述的锌乙醇脱氢酶家族。该组中22个严格保守的氨基酸几乎全部在运动发酵单胞菌乙醇脱氢酶I中也保守。乙醇脱氢酶I是一种丰富的蛋白质，尽管adhA缺乏运动发酵单胞菌其他四个高表达基因中先前报道的许多特征。adhA中的密码子使用没有高度偏向，并且包括许多pdc、adhB、gap和pgk未使用的密码子。adhA的核糖体结合区域缺乏运动发酵单胞菌其他高表达基因中发现的典型Shine-Dalgarno序列。尽管这些特征可能有助于高酶水平的表达，但它们似乎对运动发酵单胞菌adhA的表达不是必需的。
