The breakdown of the adenosine phosphates by brain tissue

Abstract

1. 1. An enzymatic method is described for the estimation of a mixture of the adenosine phosphates. 2. 2. An ionophoretic method is described for the quantitative estimation of a mixture of AMP, IMP, adenosine, and inosine. 3. 3. Homogenates of rat brain tissue can convert ATP to inosine, the main intermediates being ADP, AMP, and IMP. 4. 4. In the presence of added Mg ++ or Ca ++ ions, there is a rapid conversion of ATP to AMP followed by a slower conversion of the AMP to inosine. In the absence of either of these ions, a rapid conversion of ATP to ADP takes place resulting in the accumulation of ADP. 5. 5. It is concluded that the major pathway for the conversion of AMP to inosine in brain homogenates is via IMP rather than adenosine. 6. 6. In the presence of activating ions, the breakdown of ATP by brain mitochondria appears to be similar to that by brain homogenate. 7. 7. The following enzymes concerned in the breakdown of ATP are present in brain homogenates: adenosinetriphosphatase, myokinase, 5′-adenylic acid deaminase, adenosine deaminase, and a 5′-nucleotide phosphatase.