Oxobutyrate

L-3-metliylvaline 3, 3-dimethyl-2-oxobutyric acid + Asp transaminase Cryptococcus leurentii 197... 

Fig. 8.1 Proposed synthetic pathways for dimethylsulfoniopropionate from methionine for three algal and plant species. DMSHB 4-dimethylsulfio-2-hydroxy-butyrate, MTHB 4-methylthio-2-hydroxybutyrate, MTOB 4-methylthio-2-oxobutyrate, SMM S-methylmethionine...

This enzyme [EC 1.2.7.2], also known as 2-oxobutyrate synthase, catalyzes the reaction of o -ketobutyrate (or,... 

Ketoacid standard (3-methyl-2-oxobutyric acid, 2-ketoisovaleric) mix 50 mg in 25 ml (2 mg/ml) deionized water. Store the solution at 4°C. 

S phosphoenolpyruvate -I- histidine-containing protein <1-9, 13-15> (<1,6> in a first reaction step phosphate is transferred to the N-3 position of the imidazole ring of histidine [4, 9, 13] <6> in a second reaction step phosphate is transferred to the N-1 position of the imidazole ring of the histidine containing-protein (i.e. HPr), the phospho group of the intermediate phospho-enzyme I can also be transferred to pyruvate or 2-oxobutyrate... 

The isomeric l,2,4-triazin-5-ones also have herbicidal activity, and of these the 4-amino compounds stand out. Metribuzin (3) and metamitron (4) (68SAP6804409) possess excellent selectivity, the former being manufactured on a very large scale. Metribuzin can be synthesized from 3,3-dimethyl-2-oxobutyric acid (Scheme 3). 

The third type of carbon-branched unit is 2-oxoisovalerate, from which valine is formed by transamination. The starting units are two molecules of pyruvate which combine in a thiamin diphosphate-dependent a condensation with decarboxylation. The resulting a-acetolactate contains a branched chain but is quite unsuitable for formation of an a amino acid. A rearrangement moves the methyl group to the (3 position (Fig. 24-17), and elimination of water from the diol forms the enol of the desired a-oxo acid (Fig. 17-19). The precursor of isoleucine is formed in an analogous way by condensation, with decarboxylation of one molecule of pyruvate with one of 2-oxobutyrate. 

The latter can be converted in one pathway to lysine and in another to homoserine. Homoserine can yield either homocysteine and methionine or threonine. Although threonine is one of the end products and a constituent of proteins, it can also be converted further to 2-oxobutyrate, a precursor of isoleucine. 

When present in excess methionine is toxic and must be removed. Transamination to the corresponding 2-oxoacid (Fig. 24-16, step c) occurs in both animals and plants. Oxidative decarboxylation of this oxoacid initiates a major catabolic pathway,305 which probably involves (3 oxidation of the resulting acyl-CoA. In bacteria another catabolic reaction of methionine is y-elimination of methanethiol and deamination to 2-oxobutyrate (reaction d, Fig. 24-16 Fig. 14-7).306 Conversion to homocysteine, via the transmethylation pathway, is also a major catabolic route which is especially important because of the toxicity of excess homocysteine. A hereditary deficiency of cystathionine (3-synthase is associated with greatly elevated homocysteine concentrations in blood and urine and often disastrous early cardiovascular disease.299,307 309b About 5-7% of the general population has an increased level of homocysteine and is also at increased risk of artery disease. An adequate intake of vitamin B6 and especially of folic acid, which is needed for recycling of homocysteine to methionine, is helpful. However, if methionine is in excess it must be removed via the previously discussed transsulfuration pathway (Fig. 24-16, steps h and z ).310 The products are cysteine and 2-oxobutyrate. The latter can be oxidatively decarboxylated to propionyl-CoA and further metabolized, or it can be converted into leucine (Fig. 24-17) and cysteine may be converted to glutathione.2993... 

Ethylene is rather inert, but it is metabolized slowly, some of it to ethylene glycol.326 Plants store N-malonyl-ACC as a metabolically inert pool. Excess ACC can be deaminated in a PLP-dependent reaction to 2-oxobutyrate (step k, Fig. 24-16), a process that also occurs in bacteria able to subsist on ACC.327/327a There may also be other mechanisms for ethylene formation, e.g., peroxidation of lipids during scenescence of leaves.328 See also Chapter 31, Section G. 

As indicated in Fig. 24-17, pyruvate is the starting material for the formation of both l- and D-alanine and also the branched chain amino acids valine, leucine, and isoleucine.339,340 The chemistry of the reactions has been discussed in the sections indicated in the figure. The first step is catalyzed by the thiamin diphosphate-dependent acetohydroxyacid synthase (acetolactate synthase), which joins two molecules of pyruvate or one of pyruvate and one of 2-oxobutyrate (Fig. 24-17 Fig. 14-3).340a b In E. coli there are two isoenzymes encoded by genes ilv B and ilv HI. Both are regulated by feedback inhibition by valine, probably... 

Ruthenium catalysts that contain Cl-MeO-BIPHEMP have been used in the asymmetric hydrogenation of P-keto esters (99% ee)126 and the dynamic kinetic resolution of substituted P-keto esters (Scheme 12.33).121 The asymmetric hydrogenation of methyl 3,3-dimethyl-2-oxobutyrate to the corresponding a-hydroxy ester has been reported with ruthenium catalyst, RuBr2[(-)-Cl-MeO-BIPHEMP] 2 (Scheme 12.34).121... 

Rhodium Mandyphos catalysts have been used to reduce enamide esters and acids with enan-tioselectivities that range from 95% to 99%.175 183 185 Other applications reported are the asymmetric hydrogenation of tiglic acid and ethyl 3,3-dimethyl-2-oxobutyrate in 97% ee and >97% ee, respectively.175... 

The biosynthesis of (R)-pantothenate in E. coli [112] (see Fig. 8.22) and Coryne-hactcrium glutamicum [113] has been elucidated. 3-Methyl-2-oxobutyrate, an intermediate in the L-Val biosynthesis pathway, is successively hydroxymethylated and reduced to (R)-pantoate. The latter intermediate is coupled, in an ATP-re-quiring reaction, with 3-aminopropionate that is derived from L-aspartate via decarboxylation. The corresponding genes have been identified [114]. 

Apart from sotolon, the other compounds in Fig. 5 can be explained as the products of a Maillard reaction, and their carbon skeletons simply originate from the active Amadori intermediate in other words, they still preserve the straight carbon chain structure of monosaccharides. In spite of being a simple Cg lactone, sotolon has a branched carbon skeleton, which implies another formation process in the Maillard reaction. Sulser e al.(6) reported that ethyl sotolon (ll) was prepared from threonine with sulfuric acid, and that 2-oxobutyric acid, a degradation product of threonine, was a better starting material to obtain II. This final reaction is a Claisen type of condensation, which would proceed more smoothly under alkaline conditions. As we(lO) obtained II from 2-oxobutyric acid (see figure 6) with a high yield in the presence of potassium carbonate in ethanol, a mixed condensation of 2-oxobutyric and 2-oxo-propanoic (pyruvic) acids was attempted under the same conditions, and a mixture of sotolon (22% yield) and II were obtained however, the... 

Lantibiotics contain several unusual amino acids, including the thioether lanthionine (Lan) hnkage and its methyl substituted analog methyUanthionine (MeLan) (Fig. la) that unifies all members of the class and accounts for their family name. In addition to Lan, lantibiotics commonly contain 2,3-dehydroalanine (Dha) and (Z)-2,3-dehydrobutyrine (Dhb). In all, no less than 15 different posttranslational modifications have been documented in lantibiotics (for a selection see Fig. la), and up to 58% of their amino acids are modified. These extensive structmal alterations overcome the constraints imposed by the use of 20 amino acids in ribosomally synthesized peptides. Some less common, posttranslationally crafted residues in lantibiotics are fS-hydroxy aspartate, lysinoalanine, aminovinyl cysteine (AviCys), D-alanine, 2-oxobutyrate, 2-oxopropionate, and 2-hydroxypropionate. The presence of these unusual residues is thought to be important for the biological activity of lantibiotics. 

C7H1203 ethyl 3-methyl-2-oxobutyrate 20201-24-5 335.15 28.301 1,2 11609 C7H13CI02 2-(3-chtoropropyl)-2-methyl-1,3-dioxolane 5978-08-5 347.65 29.462 1.2... 

The pH optimum for the lactate-to-pyruvate (L—>P) reaction is 8.8 to 9.8, and an assay mixture, optimized for LD-1 at 37 °C, contains NAD% 9mmol/L, and L-lactate, 80mmol/L. For the P —> L assay, at 37 °C, the pH optimum is 7.4 to 7.8, NADH 300fJ.mol/L, and pyruvate 0.85mmol/L. The optimal pH varies with the predominant isoenzymes in the sample and depends on the temperature and on substrate and buffer concentrations. The specificity of the enzyme extends from L-lactate to various related 2-hydroxyacids and 2-oxo-acids. The catalytic oxidation of 2-hydroxybutyrate, the next higher homologue of lactate, to 2-oxobutyrate is referred to as 2-hydroxybutyrate dehydrogenase (HBD) activity. LD does not act on n-lactate, and only NAD serves as a coenzyme. 

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