Branched-chain alpha-keto acids isolated as oxime derivatives: Relationship to the corresponding hydroxy acids and amino acids in Maple Syrup Urine Disease

Comparison of the Catabolism of Branched-Chain L-Amino Acids in Cultured Human Skin Fibroblasts

“…In contrast, hydroxy acid formation from 2-0x0-4-methylpentanoate and 2-0x0-3-methylpentanoate seems negligible. This has been shown with incubated fibroblasts (22) and further evidence is provided by a variety of clinical chemical findings (23)(24)(25)(26)(27).…”

Maple Syrup Urine Disease: Analysis of Branched Chain Ketoacid Decarboxylation in Cultured Fibroblasts

“…Only small differences in the residual BCKA degradation activity were measured at 5 x M substrate concentration, which is slightly above the normal serum concentration of these substances (18). Those differences correlate to some extent with the phenotypic expression of the disease.…”

“…Since free amino acid concentrations in the culture medium (21) were as high as in plasma of M S U D patients under strict dietary control (18), maximally about 0.25 x mol endogenous substrate/assay could be expected, a figure based on data recently published (8,18). This amount appears not to be relevant for the calculation of the decarboxylation kinetics.…”

“…Lancaster et al (18) concluded from their data for the BCAA and BCKA concentrations in plasma of M S U D patients that reverse transamination in these patients was very effective when BCKA concentrations did not exceed 10-fold the normal. These in vivo findings leave open the possibility that efficient transamination and reverse transamination are produced by different and orga,lspecific transarninases (18) and they are not conclusive for the present in vitro experiments with one uniform cell type only.…”

The Relationship between the Branched Chain Amino Acids and Their α-Ketoacids in Maple Syrup Urine Disease

“…The small number of values which lay at either extreme of the range occurred a similar number of times in all subjects.Average ratios, standard deviation, and range are listed in Table 1. (10) who found that the ketoacid analogues do not accumulate until the level of each branched chain amino acid exceeds 0.8 to 1.0 mM (10.5-13 mg/dl). This conclusion was based on a small number of samples and a technique with poor recoveries of ketoacid analogues in serum, which ranged from 42 to 52%.…”