Abstract
1. Both mouse brain and mouse liver preparations were found to utilize substrates characteristic of the following carbohydrate enzyme systems : the glycogen, glucose, fructose, mannose, fructose-1-phosphate (5), oxidative pentose phosphate (4), and tricarboxylic acid system.
2. Each of these enzyme systems was found on isolated brain mitochondria and a number on isolated liver mitochondria.
3. The implications of these findings in regard to the lability, normal enzyme system complement and functions of mitochondria are discussed.