Alcohol dehydrogenases from Bacillus stearothermophilus

Firstly, let us discuss the example of a thermophilic alcohol dehydrogenase from Bacillus stearothermophilus (bsADH) studied by Kohen et al. [91, 92]. This enzyme catalyzes the abstraction of a hydride to the nicotinamide cofactor NAD+ as depicted in Fig. 6.54. The Arrhenius diagram is depicted in Fig. 6.54(a) a sudden decrease in the apparent slope and the apparent intercept of the Arrhenius curves is observed around room temperature (Fig. 6.54(b)). The puzzling observation is that the kinetic isotope effects are independent of temperature in the high-temper-ature regime but dependent on temperature in the low-temperature regime. 

In 2012, Kroutil and co-workers reported the first amination reaction of primary alcohols with ammonium chloride by an artificial multi-enzyme-catalyzed cascade method (Scheme 29) [173]. The authors assumed that the reaction might proceed by two steps. Initially, the alcohol was oxidized by an alcohol dehydrogenase (ADH), consuming NAD" " and leading to the formation of the aldehyde and NADH. Then, the aldehyde intermediate was aminated with an amine donor L-alanine by a w-transaminase (w-TA). Finally, by combining ADH-hT (ADH from Bacillus stearothermophilus) with CV-w-TA (w-TA from Chromobacterium violaceuni), the amination of various primary alcohols successfully afforded the corresponding primary amines in 2-99 % yields. 

Leuconostoc mesenteroides (4 3), Pseudomonas aeruginosa (4 4), Streptococcus mutans (435), and Bacillus stearothermophilus (486,437). The protein from the latter species was purified by Kolb and Harris (436) and found to have a free N-terminus in contrast to the liver and yeast alcohol dehydrogenases. The bacterial protein was, therefore, submitted to sequence analysis in an automatic sequenator which revealed the 45 first residues (IS). These are listed in Table XIV. It is clear that the structure of the bacterial enzyme is distantly related to those of the yeast and mammalian enzymes, but few residues are identical in all proteins at equivalent positions (Table XIV). Further aspects of this relationship are discussed in Section II,D. 

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