GUANINE-DEAMINASE ACTIVITY IN RAT BRAIN AND LIVER

TL;DRAbstract

1. Guanine deaminase in rat brain and liver was distributed among all the subcellular fractions: nuclei, ;heavy' mitochondria, ;light' mitochondria, microsomes and the supernatant fluid. The greater part of the activity passed into the soluble fraction. Among the particulate components, the ;light' mitochondria constituted the richest fraction. 2. The sum of the enzymic activities of the component fractions obtained on differential centrifugation was considerably greater than the activity of guanine deaminase in the whole homogenate. 3. The ;heavy'-mitochondrial fraction had a powerful inhibitory effect on the guanine-deaminase activity of the supernatant fraction. 4. All the sedimented fractions, except the microsomes, gave rise to higher guanine-deaminase activity on treatment with Triton X-100. 5. The inhibitory capacity of the ;heavy' mitochondria increased on treatment with Triton X-100; the detergent-treated nuclear fraction also brought about inhibition of the 5000g supernatant.

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