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Glycerol oxidation in rat brain: Subcellular localization and kinetic characteristics
Author(s) -
Tildon J. Tyson,
Roeder Lois M.
Publication year - 1980
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.490050103
Subject(s) - glycerol , mitochondrion , biochemistry , enzyme , chemistry , biology
The oxidation of [1,3‐ 14 C]glycerol to 14 CO was measured in slices, whole homogenates, and subcellular fractions of rat brain. In all of these tissue preparations, the Lineweaver‐Burk plots of glycerol oxidation were biphasic, yielding two apparent K m and V values. Similar kinetic characteristics were obtained with brain homogenates from guinea pig, mouse, rabbit, monkey, and pig. In other tissues of the rat, including heart, kidney, liver, and skeletal muscle, the Lineweaver‐Burk plots for glycerol oxidation were not biphasic but were linear. Heating the brain homogenates for five minutes at 5°C caused a 50% decrease in the rate of oxidation of glycerol without a change in the biphasic double reciprocal plot. The addition of purified glycerol kinase (EC 2.7.1.30) to the homogenate caused an increase in the rate of oxidation and resulted in a linear Lineweaver‐Burk plot. Brain mitochondria were prepared by two different methods, both of which yielded an enrichment of glycerol oxidation. In contrast, the rate of glucose oxidation was higher in homogenates than in mitochondria, and glucose competed with glycerol as substrate only extramitochondrially. The effects of various metabolic inhibitors suggested the participation of intact, coupled mitochondria, of glycolytic enzymes, and of electron transport in the oxidation of glycerol. The data support the primary localization of glycerol oxidation in nonsynaptic mitochondria in brain and the presence in that organelle of enzymes of the Embden‐Meyerhoff pathway or an as yet unidentified system for oxidizing this compound.