Comparison of hydrogenases from Clostridium butyricum and Thiocapsa roseopersicina

摘要

Properties on temperature and oxygen stability of cytoplasmic hydrogenases from fermentative strict anaerobic bacterium, Clostriciwn butyricum NCIB 9576 (Cl. butyricum) and purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 (T. roseopersicina) were compared. The optimum temperatures for growth of Cl. butyricum and T. roseopersicina were 37℃ and 25℃, respectively, while those for H_2 evolution of cytoplsmic hydrogenases prepared from Cl. butyricum (C-H_2ase) and T. roseopersicina (T-H_2ase) were 45℃ and 65℃, respectively. T-H_2ase was more thermo-stable than C-H_2ase. T-H_2ase retained its full activity for 5 hrs at 50℃ and retained 90% of its original activity for 5 hrs at 60℃, however, C-H_2ase lost its activity drastically at 50℃. The optimum pHs for H_2 oxidation of C-H_2ase and T-H_2ase were 9.0 and 7.5 respectively. The both enzymes showed maximum H_2 evolution activity at pH 7.0. Under the aerobic condition, 80% of T-H_2ase activity was retained for 10 hrs at 30℃, and 50% of activity was still remained after 6 days at the same experimental conditions. But the C-H_2ase was labile to oxygen and lost its activity immediately after the exposure to air.