Two novel metal-independent long-chain alkyl alcohol dehydrogenases from Geobacillus thermodenitrificans NG80-2

1 TEDA School of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, PR China 2 Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin 300457, PR China 3 Tianjin Research Center for Functional Genomics and Biochip, Tianjin 300457, PR China 4 The Engineering and Research Center for Microbial Functional Genomics and Detection Technology, Ministry of Education, PR China 5 The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, PR China Two alkyl alcohol dehydrogenase (ADH) genes from the long-chain alkane-degrading strain Geobacillus thermodenitrificans NG80-2 were characterized in vitro . ADH1 and ADH2 were prepared heterologously in Escherichia coli as a homooctameric and a homodimeric protein, respectively. Both ADHs can oxidize a broad range of alkyl alcohols up to at least C 30 , as well as 1,3-propanediol and acetaldehyde. ADH1 also oxidizes glycerol, and ADH2 oxidizes isopropyl alcohol, isoamylol, acetone, octanal and decanal. The best substrate is ethanol for ADH1 and 1-octanol for ADH2. For both ADHs, the optimum assay condition is at 60 °C and pH 8.0, and both NAD and NADP can be used as the cofactor. Sequence analysis reveals that ADH1 and ADH2 belong to the Fe-containing/activated long-chain ADHs. However, the two enzymes contain neither Fe nor other metals, and Fe is not required for the activity, suggesting a new type of ADH. The ADHs characterized here are potentially useful in crude oil bioremediation and other bioconversion processes. Correspondence Lu Feng fenglu63{at}nankai.edu.cn Abbreviations: ADH, (alkyl) alcohol dehydrogenase