Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1948703 | Biochimica et Biophysica Acta (BBA) - General Subjects | 2006 | 10 Pages |
Abstract
An α,β-dicarbonyl reductase activity was purified from Saccharomyces cerevisiae and identified as the cytosolic enzyme d-Arabinose dehydrogenase (ARA1) by MALDI-TOF/TOF. Size exclusion chromatography analysis of recombinant Ara1p revealed that this protein formed a homodimer. Ara1p catalyzed the reduction of the reactive α,β-dicarbonyl compounds methylglyoxal, diacetyl, and pentanedione in a NADPH dependant manner. Ara1p had apparent Km values of â¼Â 14 mM, 7 mM and 4 mM for methylglyoxal, diacetyl and pentanedione respectively, with corresponding turnover rates of 4.4, 6.9 and 5.9 sâ 1 at pH 7.0. pH profiling showed that Ara1p had a pH optimum of 4.5 for the diacetyl reduction reaction. Ara1p also catalyzed the NADP+ dependant oxidation of acetoin; however this back reaction only occurred at alkaline pH values. That Ara1p was important for degradation of α,β-dicarbonyl substrates was further supported by the observation that ara1-Î knockout yeast mutants exhibited a decreased growth rate phenotype in media containing diacetyl.
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Authors
Barry van Bergen, Rona Strasser, Normand Cyr, John D. Sheppard, Armando Jardim,