ISSN:
1432-0991
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract l-Serine dehydratase fromLactobacillus fermentum was purified 100-fold. It was stabilized by the presence of 1 mM l-cysteine in 50 mM phosphate buffer. Mr=150,000 was determined by gel filtration. The enzyme consists of four apparently identical subunits (Mr=40,000) that were observed after treatment with sodium dodecyl sulfate. The apparent Km forl-serine was 65 mM. Fe++ was required for the enzymatic activity, and the apparent Km value for this reaction was 0.55 mM. Maximum enzymatic activity was observed at 45°C and pH 8.0 in 50 mM phosphate buffer. At pH values different from the optimum, a positive cooperativity between substrate molecules was observed. The activation energy of the reaction was 11,400 and 22,800 cal × mol−1 for temperature values more than and less than 35°C respectively. The purified enzyme showed a maximum absorption between 400 and 420 nm, indicating the presence of pyridoxal-5′-phosphate (PLP) as a prosthetic group. The PLP concentration was 0.027 µmoles per milligram of protein. The data suggest that there is 1 mol of PLP for each protein subunit.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02092310
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