Abstract
A rumen protozoon, Entodinium caudatum, and mixed rumen protozoa were isolated from a monofaunated and a naturally faunated goats with rumen fistula, respectively. Diaminopimelate decarboxylase activities of the crude enzymes of the protozoa were assayed by determining the lysine production with a high-performance liquid chromatography. The optimal pH and temperature for the catalytic activities of the crude enzymes were found to be 6.3 and 50°C, respectively, in both E. caudatum and mixed rumen protozoa, while the Km values for 2, 6-diaminopimelate in both protozoal crude enzymes were 0.62 and 0.68mM, respectively. For the stability of the enzyme of E. caudatum, the presence of pyridoxal 5'-phosphate and thiol group such as 2-mercaptoethanol and dithiothreitol was necessary and higher catalytic activities were retained in the pH range of 5.0 and 6.8. The enzyme was stable when kept in the temperature range of 25 and 60°C for 10min, but the activity was completely lost at 70°C. DL-penicillamine inhibited the enzyme at a concentration of 1.6mM, but its effect was lessened by increasing the concentration of pyridoxal-5'-phosphate.
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