[Stability of hydrogenase from the purple sulfur bacteria Thiocapsa roseopersicina]

The hydrogenase from T. roseopersicina is highly resistant to the effects of urea (8 M), Me2SO (20%) and DS-Na (1%), while inactivation of the hydrogenase from Rhodopseudomonas capsulata occurs in the presence of 0.1% DS-Na. The higher the purification level of T. roseopersicina hydrogenase preparation, the higher stability it possesses (T 1/2 = 60 days, 24 degrees). The hydrogenase inactivation at 80 degrees under anaerobic conditions occurs in one stage according to the equation of first-order-reaction (k1i = 7.10(-5) sec-1), while under aerobic conditions it has two stages with a decrease in the rate of this process in the second stage (k2i = 1.8 . 10(-6) sec-1). Glycerol and NaCl do not stabilize the T. roseopersicina hydrogenase. The rate of thermal inactivation of the hydrogenase bound to the membranes, DEAE-cellulose or phenylsepharose is higher than that of the soluble enzyme. The considerable decrease of the thermal stability of the enzyme is caused by the thiol reagents: they cause irreversible denaturation of the enzyme. The hydrogenase partly inactivated under aerobic conditions is reactivated in the presence of Na2S2O4. The data obtained indicate the important role of disulphide bonds in stabilization of T. roseopersicina hydrogenase.