[Features of temperature dependence of the Na+,K+-ATPase reaction in normal and tumorous brain tissue]

It has been shown that in the enzyme preparations (EP) from normal brain tissue (NBT) a typical break on the Arrhenius plot appeared at 20-22 degrees C, nH for Na+ and K+ exceeding 1.7 and 1.4, respectively. In EP from tumoural brain tissue (TBT) no break on the Arrhenius plot at 20-22 degrees C was revealed, but it appeared at 27.5 + 30.5 degrees C. The nH for Na+ with Na+,K+-ATPase from TBT was only 0.9, but the cooperative binding of K+ was preserved (nH = 1.3). Electrophoregrams (EP) from TBT showed additional protein bands. The urea and digitonin treatment of EP from NBT induced a break on the Arrhenius plot at 27.5-30.5 degrees C. It is suggested that the break at 27.5-30.5 degrees C is, probably, accompanied by local changes in the conformation of protein components of the enzyme.