Properties of L-Serine Dehydratase in Alternaria chlamydospora

Partial purified enzyme was used in studying the properties of L-serine dehydratase (EC 4.2.1.13) of Alternaria chlamydospora. The final active preparation contained four proteins of 96, 52, 14 and 8 kDa as judged by SDS-PAGE. Maximum enzymatic activity was observed at 45 oC and pH 8.5. The enzyme was thermolabile. Km value for L-serine was 39.2 mM. The enzyme was catalyzed the deamination of DL-serine, L-alanine, glycine, L-threonine, DL-threonine and D-threonine but at slower rates than that found in L-serine. Pyridoxal phosphate stimulates the activity of L-serine dehydratase. None of tested metal salts activated the enzyme. Alternatively the enzyme activity was inhibited by Ni2+, Fe2+, Cu2+ and Zn2+. L-Cysteine inhibited L-serine dehydratase of Alternaria chlamydospora noncompetitively with a Ki of 5.4 mM. Stability of the enzyme under different conditions was investigated