2-Oxoisocaproic acid

Leucine and its branched chain ketoac-ids, such as 2-oxoisocaproic acid, in maple syrup urine disease... 

Fig. 10.1 Metabolites in the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease). Extracted using ethyl acetate and separated as their trimethylsilyl-oxime derivatives on a 25 m SE-30 capillary column, using temperature programming from 80°C to 110°C at 0.5°C min and an injection split ratio 1 12 at a temperature of 250°C. The peaks marked R are due to solvent and reagents. Peak identifications are 1, lactic 2, 2-hydroxyisobutyric 3, 2-hydroxybutyric 4, pyruvic 5, 3-hydroxybutyric 6, 2-hydroxyisovaleric 7, 2-oxobutyric 8, 2-methyl-3-hydroxy-isovaleric 10, a and b, 2-oxoisovaleric 11, acetoacetic 12, 2-hydroxyisocaproic 13, 2-hydroxy-3-methyl- -valeric 14, 2-oxo-3-methyl-/i-valeric (14a L- 14b D-) 15, 2-oxoisocaproic acids. The internal standard was malonic acid. (Redrawn with modifications from Jellum etal., 1976)...

Fig. 10.3 Chromatogram of organic acids extracted from the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease), extracted and separated as described in the legend to Fig. 10.2. The chromatogram illustrates the overlapping peaks in the regions occupied by 3-hydroxybutyric, 2-hydroxyisovaleric and 2-oxoisovaleric acids (peak 1) and 2-oxo-3-methyl-valeric, 2-hydroxyisocaprioic and 2-oxoisocaproic acids (peak 2) and phosphate (peak 3). Other peaks of interest are (4) citric, (5) 4-hydroxyphenyl-lactic, (6) 4-hydroxyphenylpyruvic, (7) n-tetracosane (standard) and (8) -hexacosane (standard). (Compare with Fig. 10.4.)...

Fig. 10.7 illustrates the metabolic pathway of L-leucine and the positions of the known enzyme deficiencies in the pathway that lead to abnormal organic acidurias. After the initial transamination to 2-oxoisocaproic acid, the keto... 

Fig. 10.5 Mass spectra of the ethoxime-trimethylsilyl derivatives of (a) 2-oxoisovaleric, (b) 2-oxo-3-methyl-n-valeric (peak 1), (c) 2-oxo-3-methyl-/i-valeric (peak 2) and (d) 2-oxoisocaproic acids and the trimethylsilyl derivatives of (e) 2-hydroxyisovaleric, (f) 2-hydroxy-3-methyl-rt-valeric and (g) 2-hydroxyisocaproic acids.

The production of oxoisovaleric acid and oxoisocaproic acids, intermediates in the biosynthesis of valine and leucine respectively, is shown in Fig. 17.16. The decarboxylation and reduction (NAD+ dependent) of these oxo-acids yields the fusel alcohols isobutanol and isoamyl alcohol (Fig. 17.16). Presumably, some oxo-acids in beer result from excretion from the pool and some aldehydes by excretion prior to reduction to the corresponding alcohol. Table 17.7 shows the chemical relationships between alcohols, aldehydes, oxo-acids and corresponding amino acids. 

Isoamyl alcohol Isovaleraldehyde a-Oxoisocaproic acid Leucine... 

Gerbling H. Peroxisomal degradation of 2-oxoisocaproate. Evidence for free acid intermediates. Bot Acta, 1993 106 380-387. 

Fig. 4.3 Chromatogram of standard oxo acids separated as their trimethysilyl-oxime derivatives on 3 per cent OV-17 using temperature programming from 110°C to 220°C. Peak identifications are 1, pyruvate 2, 2-oxobutyrate 3, 2-oxoisovalerate 4, 2-0X0valerate 5, L-2-oxo-3-methylvalerate 6, 2-oxoisocaproate plus 7, d-2-oxo-3-methylvalerate 8, 2-oxo-4-methylthiobutyrate 9, 2-oxoglutarate 10, phenylpyruvate. (Redrawn with modifications from Sternowsky etal., 1973)...

Fig. 10.4 Chromatogram of organic acids extracted from the same urine of the patient illustrated in Fig. 10.3, separated as their O-n-butyloxime and trimethylsilyl derivatives under the conditions described in the legend to Fig. 10.2. Peak identifications are 1, lactate 2, glycollate 3, unidentified 4, 2-hydroxy-n-butyrate plus 3-hydroxy-propionate 5, sulphate 6, 3-hydroxybutyrate and 3-hydroxyisobutyrate 7, 2-hydroxyisovalerate 8, 3-hydroxyisovalerate 10, 2-hydroxyisocaproate 11,2-hydroxy-3-methyl-n-valerate 12, phosphate 13,2-oxoisovalerate (peak 1) 14,2-oxoisovalerate (peak 2) 15, 2-oxo-3-methyl-/i-valerate (peak 1) 16, 2-oxo-3-methyl-n-valerate (peak 2) 17, 2-oxoisocaproate 18, citrate 19, 4-hydroxyphenyl-lactate 20, n-tetracosane (standard) 21, n-hexacosane (standard). The separation of O-n-butyloxime-TMS derivatives of the keto acids from the TMS-hydroxy acids and other components is apparent (compare with Fig. 10.3). Note the apparent loss of 4-hydroxyphenylpyruvate. (The horizontal axis represents the time elapsed in minutes from sample injection.)...

LeuDH L-Leucine, L-valine, L-branched chain amino acids, 2-oxoisovalerate, 2-oxo branched chain acids, 2-oxoisocaproate, L-methionine (methioine y-lyase), aminopeputidase, o-amino acid aminotransferase, tripeptide aminopeptidase, stereospecificity of hydrogen transfer of NADH (low substrate amino acid racemase), maple syrup urine disease, hyperinsulinemic euglycemic clamps... 

The enzyme reactor is industrially used for the asymmetric production of an unnatural amino acid, L-rerr-leucine, which is useful for syntheses of a variety of anti-AIDS and anticancer compounds, and L-[ N]leucine, which is used in the investigation of protein balance in medicine as a nonradioactive tracer [74,75]. L-ferr-Leucine is produced from 3,3-dimethylpyruvate and ammonia, and L-[ N]leucine from 2-oxoisocaproate and [ N]ammonium chloride. The thermostable B. stearothermophilus enz3une is more useful than the B. sphaericus enzyme for the industrial production due to the high stability [76]. 

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