Dehydrogenases mandelate dehydrogenase

Tsou AY, SC Ransom, JA Gerlt, DD Buechter, PC Babbitt, GL Kenyon (1990) Mandelate pathway of Pseudomonas putida sequence relationships involving mandelate racemase, (5)-mandelate dehydrogenase, and benzoylformate decarboxylase and expression of benzoylformate decarboxylase in Escherichia coli. Biochemistry 29 9856-9862. 

The mandelate pathway in Pseudomonas putida involves successive oxidation to benzoyl formate and benzoate, which is further metabolized via catechol and the 3-ketoadipate pathway (Figure 8.35a) (Hegeman 1966). Both enantiomers of mandelate were degraded through the activity of a mandelate racemase (Hegeman 1966), and the racemase (mdlA) is encoded in an operon that includes the next two enzymes in the pathway—5-mandel-ate dehydrogenase (mdlB) and benzoylformate decarboxylase (mdlC) (Tsou et al. 1990). 

The present reaction was proven to occur even when the microorganism had been grown on peptone as the sole carbon source. These results lead to the conclusion that this enzyme system is produced constitutively. In the case of man-delate-pathway enzymes in Pseudomonas putida, (S)-mandelate dehydrogenase was shown to be produced in the presence of an inducer (mandelic acid or benzoylformic acid) [5]. Thus, the expression of the present oxidizing enzyme of A. bronchisepticus is different from that of R putida. 

When the resulting mixture of benzoylformic acid and (i )-mandelic acid was treated with a cell free extract of Streptomyces faecalis IFO 12964 in the presence of NADH,the keto acid can be effectively reduced to (i )-mandelic acid (Fig. 1). Fortunately the presence of A. bronchisepticus and its metabolite had no influence on the reduction of the keto acid. The regeneration of NADH was nicely achieved by coupling the reaction with reduction by formic acid with the aid of formate dehydrogenase. As a whole, the total conversion of racemic mandelic acid to the i -enantiomer proceeded with very high chemical and optical yields. The method is very simple and can be performed in a one-pot procedure [6]. 

As all enzymes of the mandelate path are located on one operon, the other four enzymes could also be identified, cloned, and sequenced. (S)-Mandelate dehydrogenase [(S)-ManDH] features similarities to glycolate oxidase and flavocyto-chrome b2 (a lactate-DH) both are a/f-barrel proteins and require FMN as cofactor as does (S)-ManDH. It is reasonable to conclude that in this case nature has also sequestered a template that already catalyzes a chemistry similar to the desired reaction. 

The mandelate and jS-ketoadipate pathways are a good example of gene duplication, with strong evidence of the former evolving from the latter the congruence of MR and MLE, (S)-ManDH and benzoate dihydrodiol dehydrogenase, and possibly benzoyl formate decarboxylase and protocatechuate decarboxylase. 

Enzyme-catalyzed syntheses of enantiomeric pure hydroxy acids use lactate dehydrogenases (LDH E.C. 1.1.1.27) or hydroxyisocaproate dehydrogenases (HicDH). Both kinds of enzymes are available as D- or L-specific catalysts. L-specific [5, 6] LDHs as well as D-specific [7-10] LDHs favorably catalyze the reduction of pyruvate, HicDHs (and mandelate dehydrogenase, too) convert keto acids with longer aliphatic or aromatic side chains. These enzymes can be isolated from Lactobacillus strains [11-14]. 

Flavocytochromes 2 2-hydroxyacid dehydrogenases found in the inter-membrane space of yeast mitochondria where they couple oxidation of the substrate to reduction of cytochrome c. Examples include the enzymes from Saccharomyces cerevisiae and Hansenula anomala, both of which are l-lactate dehydrogenases (Chapman et al., 1998), and the enzyme from Rhodotorula graminis which is a L-mandelate dehydrogenase (Ilias et al., 1998). This article will concentrate on the flavocytochrome 2 (L-lactate cytochrome c oxidoreductase) from S. cerevisiae (Bakersi yeast), since this is by far the most studied of these enzymes (Chapman et al., 1991). Therefore, throughout this article, the term flavocytochrome 2 will refer specifically to the enzyme from S. cerevisiae unless otherwise stated. 

Sinclair, R. Reid, G., and Chapman, S. K., 1998, Re-design of Saccharomyces cerevisiae flavocytochrome fcj introduction of L-mandelate dehydrogenase activity, Biochem. J. 333 117nl20. 

Certain transition metal complexes exhibit activating properties and act with turnover on the metal center analogously to the catalytically active zinc ion in the active center of liver alcohol dehydrogenase. Various chiral europium shift reagents, for example Eu(hfc)3, induce reduction of (9b) by 1,4-dihydroni-cotinamides. Turnovers of about 100 are obtained on the metal complexes and methyl mandelate is formed with enantiomeric excesses of 25-44%. ... 

Mandel S, Grunblatt E, Riederer P, Amariglio N, Jacob-Hirsch J, Rechavi G, Youdim MB (2005) Gene expression profiling of sporadic Parkinson s disease substantia nigra pars compacta reveals impairment of ubiquitin-proteasome subunits, SKPIA, aldehyde dehydrogenase, and chaperone HSC-70. Ann N Y Acad Sci 1053 356-375. 

Mandelic acid Benzoylformic acid Hydroxyisocaproate dehydrogenase... 

Benzaldehyde can be produced from benzoyl formate with whole cells of Pseudomonas putida ATCC 12633 as biocatalyst119 201 (Fig. 16.6-5). Alternatively, but less effectively, mandelic acid can be used as starting material. A pH of 5.4 was found to be optimal for benzaldehyde accumulation. At this proton concentration, partial inactivation of the benzaldehyde dehydrogenase isoenzymes and activation of the benzoyl formate decarboxylase are reported. Fed-batch cultivation prevented substrate inhibition. In situ product removal is necessary to prevent product inhibition. 

This reaction has recently been improved by the use of isolated mandelate dehydrogenase from Lactobacillus curvatus314 or Streptococcus faecalis315 in a membrane reactor. 

Fig. 6.4.2 Asymmetric reductions catalyzed by mandelate dehydrogenase and alcohol...

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