Enoate reductases -and

Flail M, Stueckler C et al (2008) Asymmetric bioreduction of activated C=C bonds using Zymomonas mobilis NCR enoate reductase and old yellow enzymes OYE 1-3 from yeasts. Eur J Org Chem 2008 1511-1516... 

Values are based on the fixed Euro DKR exchange rate, 2006 data taken from the Novozymes stock report Chaparro-Riggers, J.F., Rogers, T.A., Vazquez-Figueroa, E., Polizzi, KM. and Bommarius, A.S. (2007) Comparison of three enoate reductases and their potential use for biotransformations. Adv. Synth. Catal., 349, 1521. 

From a practical point of view very selective reactions are possible. As already mentioned the CC-double bond of /7-nitro-cinnamic acid can be reduced with enoate reductase and NADH without attacking the nitro group. 

CHO Ph Enoate reductase and HLADH° NADH Ethanol CHjOH Ph 53... 

Stereospecific deuterations of 2-enoates (14,15,29,30,40) have to be carried out in H20 buffer with freeze dried cells (Table 5). Freeze drying under exclusion of oxygen leads to cells without loss of enzyme activity if again under anaerobic conditions 1 g wet packed cells is slowly stirred or shaken with 0,5 ml of a 10 pM solution of potassimn hexacyanoferrate-III for 20 minutes at 35 C. Under these conditions enoate reductase and probably also hydrogenase are transferred into the oxidized state. 

Scheme 4.21 Synthesis of two diastereoisomers of dihydrocarveol through a one-pot system employing an enoate reductase and a reductase.

Activated alkene reduction a, -Unsaturated aldehyde, ketone, ester Saturated aldehyde, ketone, ester Asymmetric reduction of C = C bonds Alkene reductase (also known as enoate reductase and ene-reductase)... 

NAD(P)H-dependent catalytic reduction reactions such as carbonyl or enoate reductases and hydroxy acid or amino acid dehydrogenases [14],... 

Rohdish F, A Wiese, R Feicht, H Simon, A Bacher (2001) Enoate reductases of Clostridia. Cloning, sequencing, and expression. J Biol Chem 276 5779-5787. 

Buhler M, H Simon (1982) On the kinetics and mechanism of enoate reductase. Hoppe-Seylers Z physiol Chemie 363 609-625. 

Caldeira J, R Feicht, H White, M Teixeira, JJG Moura, H Simon, I Moura (1996) EPR and Mdssbauer spectroscopic studies on enoate reductase. J Biol Chem 271 18743-18748. 

Steinbacher, S., Stumpf, M., Weinkauf, S. et al. (2002) Enoate reductase family. In Flavins and Flavoproteins (2002), Proceedings of the 14th International Symposium, Cambridge, United Kingdom, July 14—18, pp. 941-949. 

Stuermer, R., Hauer, B., Hall, M. and Faber, K. (2007) Asymmetric bioreduction of activated C C bonds using enoate reductases from the old yellow enzyme family. Current Opinion in Chemical Biology, 11, 203-213. 

Another approach to preparing enantiomerically pure carboxylic acids and related compounds is via enanhoselective reduction of conjugated double bonds using NAD(P)H-dependent enoate reductases (EREDs EC 1.3.1.X), members of the so-called Old Yellow Enzyme family [44]. EREDs are ubiquitous in nature and their catalytic mechanism is well documented [45]. They contain a catalytic flavin cofactor and a stoichiometric nicotinamide cofactor which must be regenerated (Scheme 6.23). 

Simon and collaborators have described a novel stereoselective electroenzymatic reduction of alkenes of type 23 (equation 12)28. The enzyme enoate reductase is the reductant... 

Enoate reductase [153, 154], which occurs in strains of Clostridium or Proteus, and 2-oxo-acid reductase [155] from Proteus vulgaris or P. mirabilis catalyzes the stereospecific reduction of substrates performed directly by reduced methyl-viologen. No nicotinamide coenzyme is required. Methylviologen is regenerable electrochemically. Examples of the reduction of enoates, ketones, and 2-oxo acids are given in [155]. 

The generation of stereogenic centers by asymmetric reduction of carbon-carbon double-bonds is a current topic in chemoenzymatic synthesis. Though enzymes of the old yellow enzyme (OYE) family were identified to perform alkene reduction and were characterized some years ago [133-135], applications of enoate reductases in natural product syntheses are still rare. Thus, potential applications are also shown in this chapter. With an increasing number of new enoate reductases, such as YqjM reductase from B. subtilis, more and more possible targets for biotransformations can be found. 

Reductions catalyzed by enoate reductase enantioselective hydrogenation of a, /6-unsaturated enoates and comparable compounds. 

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