Abstract:The potential utility of the L-lactate dehydrogenase of Bacillusstearothermophilus (BSLDH) for stereospecific, preparative-scale reductions of α-keto acids to (S)-α-hydroxy acids of > 99% ee has been demonstrated. BSLDH is a stable, thermophilic, enzyme whose gene has been cloned into a high-expression vector to assure its plentiful supply. Its specificity for keto acid substrates possessing straight- and branched-chain alkyl, cyclopropyl, or phenyl groups has been evaluated in preparative and kinetic terms… Show more
“…Based on the S-stereochemistry of the (S)-hydroxyglutaric acid present in methanopterin and the (S)-lactic acid present in coenzyme F 420 , it is likely that each is formed by the reduction of the corresponding ␣-keto acid by a NAD(P)H-dependent dehydrogenase related to the lactate/malate dehydrogenase group of enzymes (1,3,9). Likewise, it could be argued, again based on stereochemical grounds, that the oxidation of (S)-sulfolactate to sulfopyruvate occurring during the biosynthesis of coenzyme M could also be carried out by an enzyme related to the lactate/ malate dehydrogenases.…”
mentioning
confidence: 99%
“…Taking into account the lack of specificity of many of the known dehydrogenases (3,15,37), we considered it likely that one or more of these archaeal enzymes may be the enzyme(s) used for producing one or more of the (S)-␣-hydroxy acids required for the biosynthesis of methanoarchaeal coenzymes.…”
Two putative malate dehydrogenase genes, MJ1425 and MJ0490, from Methanococcus jannaschii and one from Methanothermus fervidus were cloned and overexpressed in Escherichia coli, and their gene products were tested for the ability to catalyze pyridine nucleotide-dependent oxidation and reduction reactions of the following ␣-hydroxy-␣-keto acid pairs: (S)-sulfolactic acid and sulfopyruvic acid; (S)-␣-hydroxyglutaric acid and ␣-ketoglutaric acid; (S)-lactic acid and pyruvic acid; and 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid and 1-oxo-1,3,4,6-hexanetetracarboxylic acid. Each of these reactions is involved in the formation of coenzyme M, methanopterin, coenzyme F 420 , and methanofuran, respectively. Both the MJ1425-encoded enzyme and the MJ0490-encoded enzyme were found to function to different degrees as malate dehydrogenases, reducing oxalacetate to (S)-malate using either NADH or NADPH as a reductant. Both enzymes were found to use either NADH or NADPH to reduce sulfopyruvate to (S)-sulfolactate, but the V max /K m value for the reduction of sulfopyruvate by NADH using the MJ1425-encoded enzyme was 20 times greater than any other combination of enzymes and pyridine nucleotides. Both the M. fervidus and the MJ1425-encoded enzyme catalyzed the NAD ؉ -dependent oxidation of (S)-sulfolactate to sulfopyruvate. The MJ1425-encoded enzyme also catalyzed the NADH-dependent reduction of ␣-ketoglutaric acid to (S)-hydroxyglutaric acid, a component of methanopterin. Neither of the enzymes reduced pyruvate to (S)-lactate, a component of coenzyme F 420 . Only the MJ1425-encoded enzyme was found to reduce 1-oxo-1,3,4,6-hexanetetracarboxylic acid, and this reduction occurred only to a small extent and produced an isomer of 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid that is not involved in the biosynthesis of methanofuran c. We conclude that the MJ1425-encoded enzyme is likely to be involved in the biosynthesis of both coenzyme M and methanopterin.The biosynthesis of the methanogenic cofactors coenzyme M (2-mercaptoethanesulfonic acid), methanopterin, coenzyme F 420 , and methanofuran c (Fig. 1) requires the generation of an ␣-hydroxy acid that either becomes a component in the final structure or serves as an intermediate in the formation of the coenzyme. In the case of coenzyme M, (S)-sulfolactate, formed from phosphoenolpyruvate (PEP) and bisulfite, is an intermediate in the biosynthesis (28-30). In the case of methanopterin (24, 25) and several related modified folates (33,34,36), (S)-hydroxyglutaric acid (23) is incorporated into the coenzyme during its biosynthesis (32, 35). For coenzyme F 420 (6) and its ␥-polyglutamate derivatives (7, 8, 18), (S)-hydroxypropionic acid (S-lactic acid) becomes a part of the final structure. Finally, two (1R)-diastereomers of 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid (HHTCA) serve as intermediates in the biosynthesis of the 1,3,4,6-hexanetetracarboxylic acid (HTCA) moiety of methanofuran (17; unpublished results), and another diastereomer of HHTCA [(1S)-HHTCA] is a component of metha...
“…Based on the S-stereochemistry of the (S)-hydroxyglutaric acid present in methanopterin and the (S)-lactic acid present in coenzyme F 420 , it is likely that each is formed by the reduction of the corresponding ␣-keto acid by a NAD(P)H-dependent dehydrogenase related to the lactate/malate dehydrogenase group of enzymes (1,3,9). Likewise, it could be argued, again based on stereochemical grounds, that the oxidation of (S)-sulfolactate to sulfopyruvate occurring during the biosynthesis of coenzyme M could also be carried out by an enzyme related to the lactate/ malate dehydrogenases.…”
mentioning
confidence: 99%
“…Taking into account the lack of specificity of many of the known dehydrogenases (3,15,37), we considered it likely that one or more of these archaeal enzymes may be the enzyme(s) used for producing one or more of the (S)-␣-hydroxy acids required for the biosynthesis of methanoarchaeal coenzymes.…”
Two putative malate dehydrogenase genes, MJ1425 and MJ0490, from Methanococcus jannaschii and one from Methanothermus fervidus were cloned and overexpressed in Escherichia coli, and their gene products were tested for the ability to catalyze pyridine nucleotide-dependent oxidation and reduction reactions of the following ␣-hydroxy-␣-keto acid pairs: (S)-sulfolactic acid and sulfopyruvic acid; (S)-␣-hydroxyglutaric acid and ␣-ketoglutaric acid; (S)-lactic acid and pyruvic acid; and 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid and 1-oxo-1,3,4,6-hexanetetracarboxylic acid. Each of these reactions is involved in the formation of coenzyme M, methanopterin, coenzyme F 420 , and methanofuran, respectively. Both the MJ1425-encoded enzyme and the MJ0490-encoded enzyme were found to function to different degrees as malate dehydrogenases, reducing oxalacetate to (S)-malate using either NADH or NADPH as a reductant. Both enzymes were found to use either NADH or NADPH to reduce sulfopyruvate to (S)-sulfolactate, but the V max /K m value for the reduction of sulfopyruvate by NADH using the MJ1425-encoded enzyme was 20 times greater than any other combination of enzymes and pyridine nucleotides. Both the M. fervidus and the MJ1425-encoded enzyme catalyzed the NAD ؉ -dependent oxidation of (S)-sulfolactate to sulfopyruvate. The MJ1425-encoded enzyme also catalyzed the NADH-dependent reduction of ␣-ketoglutaric acid to (S)-hydroxyglutaric acid, a component of methanopterin. Neither of the enzymes reduced pyruvate to (S)-lactate, a component of coenzyme F 420 . Only the MJ1425-encoded enzyme was found to reduce 1-oxo-1,3,4,6-hexanetetracarboxylic acid, and this reduction occurred only to a small extent and produced an isomer of 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid that is not involved in the biosynthesis of methanofuran c. We conclude that the MJ1425-encoded enzyme is likely to be involved in the biosynthesis of both coenzyme M and methanopterin.The biosynthesis of the methanogenic cofactors coenzyme M (2-mercaptoethanesulfonic acid), methanopterin, coenzyme F 420 , and methanofuran c (Fig. 1) requires the generation of an ␣-hydroxy acid that either becomes a component in the final structure or serves as an intermediate in the formation of the coenzyme. In the case of coenzyme M, (S)-sulfolactate, formed from phosphoenolpyruvate (PEP) and bisulfite, is an intermediate in the biosynthesis (28-30). In the case of methanopterin (24, 25) and several related modified folates (33,34,36), (S)-hydroxyglutaric acid (23) is incorporated into the coenzyme during its biosynthesis (32, 35). For coenzyme F 420 (6) and its ␥-polyglutamate derivatives (7, 8, 18), (S)-hydroxypropionic acid (S-lactic acid) becomes a part of the final structure. Finally, two (1R)-diastereomers of 1-hydroxy-1,3,4,6-hexanetetracarboxylic acid (HHTCA) serve as intermediates in the biosynthesis of the 1,3,4,6-hexanetetracarboxylic acid (HTCA) moiety of methanofuran (17; unpublished results), and another diastereomer of HHTCA [(1S)-HHTCA] is a component of metha...
“…Although the pathway analysis did not recognize 2‐hydroxyisovaleric acid as a metabolite in the valine degradation pathway, 2‐hydroxyisovaleric acid was directly produced from α‐ketoisovaleric acid (Bur et al . ). 2‐hydroxyisovaleric acid is excreted through urine; this urinary excretion is increased in patients with some metabolic diseases including ketoacidosis and maple syrup urine disease in humans (Landaas & Jakobs ; Magni et al .…”
Long-distance transportation is sometimes inevitable in the beef industry because of the geographic separation of major breeding and fattening areas. Long-distance transportation negatively impacts production and health of cattle, which may, at least partly, result from the disturbance of metabolism during and after transportation. However, alteration of metabolism remains elusive in transported cattle. We investigated the effects of transportation on the metabolomic profiles of Holstein steer calves. Non-targeted analysis of serum concentrations of low molecular weight metabolites was performed by gas chromatography mass spectrometry. Transportation affected 38 metabolites in the serum. A pathway analysis suggested that 26, 10, and 10 pathways were affected immediately after transportation, and 3 and 7 days after transportation, respectively. Some pathways were disturbed only immediately after transportation, likely because of feed and water withdrawal during transit. Nicotinate and nicotinamide metabolism, and citric acid cycle were affected for 3 days after transportation, whereas propionate metabolism, phenylalanine and tyrosine metabolism were affected throughout the experiment. Four pathways were not affected immediately after transportation, but were altered thereafter. These results suggested that many metabolic pathways had marked perturbations during transportation. Metabolites such as citric acid, propionate, tyrosine and niacin can be candidate supplements for mitigating transportation-induced adverse effects.
“…It could be increased to a maximum of 87% ee when one full equivalent of ( R )-oxazaborolidine was used. The absolute stereochemistry of propargyl alcohol 8 was determined by degradation via ozonolysis to known 2-cyclopropyl-2-hydroxyacetic acid. , 2 …”
Several new inhibitors of dihydrofolate reductase (DHFR) have recently progressed into clinical development due to their potent anticancer and antibiotic properties. 1,2 For the treatment of bacterial diseases, DHFR inhibitors such as trimethoprim are often applied in combination with a sulfonamide (Bactrim, Septra). Representative clinical applications include the treatment of urinary tract infections, bronchial infections, and pneumonia. 2 Chromene 1 was recently reported to have submicromolar activities against pathogenic microorganisms such as Staphylococcus aureus and Pseudomonas carinii ( Figure 1). 3 Since only racemic 1 was evaluated for biological activity and the reported synthetic strategy was limited to the preparation of racemic products, we embarked on an enantioselective synthesis of this interesting lead structure.Chromenes have been obtained by the cyclization of allylic ethers using Grubbs' ruthenium catalyst. 4 An attractive aspect of this methodology is the use of a chiral ether of type 3 for the installation of the stereocenter at C(2) of chromene 2 (Scheme 1). 5 Allyl ether 3 could be obtained from a Mitsunobu displacement with phenol 4, and the vinyl substituent appeared to be readily derived by an organometallic coupling of a halogenated derivative of 5. In this paper, we report the successful realization of this strategy, albeit with less than the desired high enantioselectivity due to an unexpectedly facile chromene photoracemization process.
Results and DiscussionThe polysubstituted o-bromophenol 7 was synthesized in two steps from commercially available 3-hydroxy-4,5-dimethoxybenzoic acid (6) according to Tanaka's protocol (Scheme 2). 6 Stille-coupling of 7 with tributylvinyltin provided styrene 4 in 81% yield. Subsequent Mitsunobu reaction 7 with carbinol (R)-8 in the presence of triethylamine 8 provided the allylic ether 9 in 66% yield. The propargyl alcohol 8 was prepared by Friedel-Crafts acylation 9 of bis(trimethylsilyl)acetylene with cyclopropanecarbonyl chloride followed by asymmetric reduction (1) Balasubramanian, B. N.; Kadow, J. F.; Kramer, R. A.; Vyas, D. Visser, M. S.; Weatherhead, G. S.; Hoveyda, A. H. J. Am. Chem. Soc. 1998, 120, 8340. (5) For the use of kinetic resolution or chromatographic separation of chiral chromenes, see: (a) Vander Velde, S. L.; Jacobsen, E. N. J. Org. Chem. 1995, 60, 5380. (b) Loncartomaskovic, L.; Mintas, M.; Trotsch, T.; Mannschreck, A. Enantiomer 1997, 2, 459. Chiral chromene was also obtained from dehydrogenation of chromane and cyclization of an R, -unsaturated sulfoxide: (c) Stocker, A.; Netscher, T.; Rü ttimann, A.; Mü ller, R. K.; Schneider, H.; Todaro, L. J.; Derungs, G.; Woggon, W.-D.
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