Abstract
Whether the impaired branched-chain 2-oxo acid dehydrogenase (BCOA-DH) activity in MSUD is concurrently or rather differentially reduced against the different 2-oxo acid substrates was assessed by measuring the 14CO2 release in 90-min incubations of cultured human skin fibroblasts with 1-14C-labeled branched-chain L-amino acids (BCAA) at 1 mmol/l.
In controls (5 strains), 14CO2 was in the order val > ile ≥ leu > allo-ile and amounted to about 8, 6, 5, and 2 nmol/90 min per mg of cell protein. In the MSUD cell lines JA, TE, MO (variants), JK. and NO (classical), residual BCOA-DH activity (as compared to 14CO2 release in controls = 100%) with val, ile, leu, and allo-ile amounted to about 6, 10, 7, and 30%, to 7, 8, 9, and 35%, to 2, 2, 4, and 9%, to 2, 3, 4, and 20% and to 2, 4, 3, and 37%, respectively. These differences could not be attributed to different BCAA transamination rates.
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Blasts, F., Schadewaldt, P. & Wendel, U. 15 DIFFERENTIALLY IMPAIRED OXIDATION OF BRANCHED-CHAIN AMINO ACIDS IN MAPLE SYRUP URINE DISEASE (MSUD). Pediatr Res 24, 263 (1988). https://doi.org/10.1203/00006450-198808000-00041
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DOI: https://doi.org/10.1203/00006450-198808000-00041