Magnesium-Adenosine Triphosphatase Activated by a Low Concentration of Calcium in Brain Microsomes

Abstract

1. The distribution of the strophanthin-sensitive ATPase (SS-ATPase) and the Mg+Ca-ATPase, and the effect of deoxycholate (DOC) on these enzymes activities, were investigated in several fractions of pig brain. 2. The presence of the Mg+Ca-ATPase in the brain microsomal fraction was clearly shown. It was also shown that the Mg+Ca-ATPase was very similar to the SS-ATPase in its distribution pattern in several fractions of the brain homogenate and in its sensitivity to DOC. 3. The microsomal fraction extracted with 0.1% DOC solution exhibited high Mg+Ca-ATPase activity and high SS-ATPase activity. For maximum activity of the strophanthin-insensitive ATPase, 3×10⁻⁵ M Ca was necessary in the presence of 2×10⁻³ M Mg, and 4×10⁻³ M Mg was necessary in the presence of 3×10⁻⁵ M Ca.