Thermoanaerobium brockii

Other biocatalysts were also used to perform the dynamic kinetic resolution through reduction. For example, Thermoanaerobium brockii reduced the aldehyde with a moderate enantioselectivity [30b,c], and Candida humicola was found, as a result of screening from 107 microorganisms, to give the (Jl)-alcohol with 98.2% ee when ester group was methyl [30dj. 

Alcohol dehydrogenase (TBADH) from Thermoanaerobium brockii [20]... 

Besides the electrochemical application, the (Cp )Rh(bpy)-complex 9 can also be used to reduce cofactors with hydrogen. In a recent study it was compared with ruthenium complex 13 [RuC12(TPPTS)2]2 (TPPTS tris(w-sulfonatophenyl)-phosphine Scheme 43.5). Both complexes were used to regenerate the cofactors in the reduction of 2-heptanone to (S)-2-heptanol, catalyzed by an ADH from Thermoanaerobium brockii (TfrADH) [46, 47]. The TON for both catalysts was 18. 

Because the direct electrochemical oxidation of NAD(P)H has to take place at an anode potential of + 900 mV vs NHE or more, only rather oxidation-stable substrates can be transformed without loss of selectivity—thus limiting the applicability of this method. The electron transfer between NADH and the anode may be accellerated by the use of a mediator. At the same time, electrode fouling which is often observed in the anodic oxidation of NADH can be prevented. Synthetic applications have been described for the oxidation of 2-hexene-l-ol and 2-butanol to 2-hexenal and 2-butanone catalyzed by yeast alcohol dehydrogenase (YADH) and the alcohol dehydrogenase from Thermoanaerobium brockii (TBADH) repectively with indirect electrochemical... 

Alcohol dehydrogenase-catalyzed reduction of ketones is a convenient method for the production of chiral alcohols. HLAD, the most thoroughly studied enzyme, has a broad substrate specificity and accommodates a variety of substrates (Table 11). It efficiently reduces all simple four- to nine-membered cyclic ketones and also symmetrical and racemic cis- and trans-decalindiones (167). Asymmetric reduction of aliphatic acyclic ketones (C-4-C-10) (103,104) can be efficiently achieved by alcohol dehydrogenase isolated from Thermoanaerobium brockii (TBADH) (168). The enzyme is remarkably stable at temperatures up to 85°C and exhibits high tolerance toward organic solvents. Alcohol dehydrogenases from horse liver and T. brockii... 

Organisms Lactobacillus kefir DSM 20587, Saccharomyces cerevisiae, Candida magnoliae, Bacillus megaterium, Thermoanaerobium brockii, Clostridium beijerinckii, Thermoanaerobacter ethanolicus, Rhodococcus ruber DSM 44541. Solvents ace = acetone iPr = i-PrOH. Substrates WM Wieland-Miescher ketone 4-Me-HP 4-methyl Hajos-Parrish ketone COBE ethyl 4-chloro-3-oxobutanoate. 

Using isolated enzymes instead of whole cells, similar problems are to be considered only in a few cases. ADH from Thermoanaerobium brockii shows varying enantiomeric excess of the product depending on the structure of the ketone to be reduced. Conversions with this enzyme yield in products with low (20% for the reduction of acetophenone) or high ee value (100% for the reduction of p-Cl-acetophenone). Predictions about the stereospecificity of HLADH catalyzed reductions can be made for simple acyclic substrates applying Prelog s rule [37] and for more complex compounds using the cubic-space model developed by Jones and Jakovac [38],... 

LKADH [86] (Lactobacillus kefir)a) TBADH [87, 88] (Thermoanaerobium brockii) Propandiol dehydrogenase [89] (E. coli)... 

Chaen, H., Nishimoto, T., Yamamoto, T., Nakada, T., Fukuda, S., Sugimoto, T., Kurimoto, M., and Tsujisaka, Y. 1999. Formation of a nonreducing trisaccharide, selaginose, from trehalose by a cell-free system of Thermoanaerobium brockii. J. Appl. Glycosci, 46,129-134. 

Ben-Bassat A., Lamed R., and Zeikus J. G. (1981) Ethanol production by thermophilic bacteria metabolic control of end product formation in Thermoanaerobium brockii. J. Bacteriol. 146, pp. 192-199. 

The suitability of the maltodextrin based phase systems could be questioned given the ubiquity of starch degrading enzymes in crude microbial extracts. In the test in which crude yeast enzyme extracts are used, there is little problem since yeast do not possess the necessary enzymes for breaking down starch. Partitioning experiments conducted on the crude extract of Thermoanaerobium brockii showed that no significant change in phase behavior occurs over the course of 2-6 hrs. 

Enzyme 1 = Enzyme 2 For example alcohol dehydrogenase from Thermoanaerobium brockii 1,, 9I, Pseudomonas spj6 Lactobacillus kefir[ 1, and Geotrichum candidum120, 211. 

The availability of sufficient quantities of enzymes for crystallization studies has led to the crystal structures been obtained for several dehydrogenases. For example, two tetrameric NADP+-dependent bacterial secondary alcohol dehydrogenases from the mesophilic bacterium Clostridium beijerinckii and the thermophilic bacterium Thermoanaerobium brockii have been crystallized in the apo- and the holo-enzyme forms, and their structures are available in the Protein Data Bank11451. The crystal structure of the alcohol dehydrogenase from horse liver is also available[40 21. 

The alcohol dehydrogenase from Thermoanaerobium brockii is very suitable for the reduction of aliphatic ketones[18, 19L Even very simple aliphatic ketones can be reduced enantioselectively. An interesting substrate size-induced reversal of enantio-selectivity was observed. The smaller substrates (methyl ethyl, methyl isopropyl or methyl cyclopropyl ketones) were reduced to the (R)-alcohols, whereas higher ketones produced the (S -enantiomers. 

Figure 16.4-3. Aldehyde dismutase acitivity of Thermoanaerobium brockii alcohol dehydrogenase (TBADH). A high affinity of the TBADH-NAD+ complex for hydrated acetaldehyde is proposed, explaining the stochiometric acetaldehyde dismutation.

PLE Pig liver YADH TBADH HLADH Yeast Thermoanaerobium brockii Horse liver... 

Alcohol Dehydrogenase Origin Thermoanaerobium brockii Fluka... 

---