Cyclic AMP independent protein kinase activity in rat cerebral cortex synaptic vesicles--partial characterization.

The intrinsic protein kinase activity of a highly purified synaptic vesicle preparation was characterized. The time-course of the reaction was found to be rapid and linear for about 1 min, but plateaued after 30 min by which time approximately 1 nmol of 32P per mg protein was incorporated into trichloroacetic acid precipitated vesicular protein. The enzyme was optimally active at pH 6.0 (37 degrees C), and had apparent Km values of 40 and 88 microM for ATP and GTP respectively. The enzyme was not stimulated by cAMP or cGMP. Mg2+ was required for maximal activity. The reaction was inhibited by free Ca2+, and non-selectively by Na+, K+, and NH4+.