ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract An NADP+–dependent reversible 3-hydroxycarboxylate oxidoreductase present in Clostridium tyrobutyricum has been purified. As judged by gel electrophoresis the enzyme was pure after a 940-fold enrichment by four chromatographic steps. Its molecular mass was estimated to be 40–43 kDa. The enzyme was most active at pH 4.5 in the reduction of 3-oxobutyrate. Other substrates were 3-oxovalerate, 3-oxocaproate, 3-oxoisocaproate and 4-chloro-3-oxobutyrate. Except for the latter all substrates were converted enantioselectively to (S)-3-hydroxy acids in the presence of NADPH. 4-Chloro-3-oxobutyrate was reduced to the (R)-3-hydroxy acid. The specific activity of the enzyme was about 1400 μmol min–1 mg–1 protein for the reduction of 3-oxobutyrate at pH 5.0. The Michaelis constant (K m) values for 3-oxobutyrate, 3-oxovalerate and 3-oxocaproate were determined to be 0.22, 1.6 and 3.0 mM, respectively. The K m values for dehydrogenation of (S)-3-hydroxybutyrate, (S)-3-hydroxyvalerate and (S)-3-hydroxycaproate were found to be 2.6, 1.1 and 5.2 mM, respectively. The identity of 43 of the first 45 N-terminal amino acid residues has been determined. So far such enzyme activities have been described in eucaryotes only.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002530050214
