[Thermostability of brain Na+, K+ -ATPase in the presence of surface-active agents].

Stability of Na+, K+-ATPase (EC 3.6.1.3) of the brain microsomal fraction towards thermoinactivation was studied under the effect of surfactants--alkyl sulphates with the C8-C15 chain length of a hydrocarbon radical, desoxycholate, triton X-100, twin-80 and digitonin. It is shown that NaCl treatment of the enzyme before thermoinactivation, and also in the presence of surfactants, increases its resistance to the effect of temperature (octyl and decyl sulphates are an exception, in their presence transport ATPase preincubated with NaCl is completely inactivated). In the presence of most surfactants used in the maximum activating concentrations the activity of Na+, K+-ATPase remained at a considerably high level (80-110% of the initial one) and did not change essentially under NaCl pretreatment of the enzyme. Besides octyl and decyl sulphate, desoxycholate, was also an exception, in the presence of NaCl it inhibited sharply the Na+, K+-ATPase activity. An interrelation is found between the ability of surfactants to decrease the activity of transport ATPase and to solubilize proteins and lipids from the microsomal fraction.