Ornithine decarboxylase activity associated with a particulate fraction of brain

Abstract

The enzymic decarboxylation of ornithine by adult rat brain largely occurs in the particulate fraction. The activity is primarily due to omithine decarboxylase (ODC) as evidenced by several criteria: i) the concurrent production of equimolar amounts of C0 2 and putrescine, ii) the sensitivity of the reaction to difluoromethylomithine (DFMO), a specific inhibitor of ODC, iii) the lack of major effect of two inhibitors of omithine-2-oxo-acid transaminase, upon the DFMO-sensitive component of decarboxylation, iv) the failure to profoundly reduce decarboxylation activity in the presence of a large excess of many aminoacids which could compete for non-specific decarboxylases. The insoluble ODC activity appears largely within synaptosomal and mitochondrial-enriched morphological fractions, yet cannot be attributed to trapped soluble ODC. Particulate ODC has a pH optimum and kinetic parameters that differ from those of soluble cerebral ODC.

Effect of trimethyltin on ornithine decarboxylase in various regions of the mouse brain

“…This correction for non-specific decarboxylation was less than 15% of total counts. The activity of frozen samples was around 70% of the corresponding value of tissues that had not been frozen [21].…”

Ornithine Decarboxylase in Human Brain: Influence of Aging, Regional Distribution, and Alzheimer's Disease

“…The specific activity of ODC was determined by measuring the rate of evolution of ' 4C0 2 from the decarboxylation of radiolabeled substrate by a method similar to that previously described (Bondy, 1986) with modification. In brief, brain tissue was dissected, weighed, and sonicated in 10 volumes of 0.32 M sucrose containing 5 mM dithiothreitol.…”