f The catabolism of branched-chain amino acids occurs via 2-oxoacid dehydrogenase in Saccharomyces cerevisiae
- Authors: J. Richard Dickinson*, Ian W. Dawes
- *Author for correspondence. Permanent address: School of Pure and Applied Biology, University of Wales College of Cardiff, PO Box 915, Cardiff CF1 3TL, UK. Tel. (0222) 874000 ext. 5762; fax (0222) 874305.
- First Published Online: 01 October 1992, Microbiology 138: 2029-2033, doi: 10.1099/00221287-138-10-2029
- Subject: Physiology And Growth
- Issue Published:
Saccharomyces cerevisiae possesses 2-oxoacid dehydrogenase (EC 126.96.36.199) similar to that found in mammalian cells. The activity is readily detected in cells which have been cultured in a minimal medium containing a branched-chain amino acid. Mutants defective in lipoamide dehydrogenase also lack 2-oxoacid dehydrogenase and are thus unable to catabolize branched-chain amino acids: 2-oxoacids accumulate in the cultures of these cells. The 2-oxoacid dehydrogenase activity is distinct from both 2-oxoglutarate dehydrogenase and pyruvate dehydrogenase, because it could not be detected in assay conditions which permitted the measurement of 2-oxoglutarate dehydrogenase and vice versa. In addition, a strain lacking 2-oxoglutarate dehydrogenase (kgd1::URA3) retained 2-oxoacid dehydrogenase as did a mutant specifically lacking pyruvate dehydrogenase (pda1::Tn5ble). In complex media the specific activity of this enzyme is highest in YEP (yeast extract-peptone)-glycerol and lowest in YEP-acetate and YEP-fructose. 2-Oxoacid dehydrogenase could not be detected in cells which had been transferred to sporulation medium. These results suggest that in S. cerevisiae the catabolism of branched-chain amino acids occurs via 2-oxoacid dehydrogenase, not via the ‘Ehrlich Pathway’.
© Society for General Microbiology, 1992 | Published by the Microbiology Society
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