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Ontogeny and Cellular Localization of the Pyruvate Recycling System in Rat Brain
Author(s) -
Cruz Fátima,
Scott Steve R.,
Barroso Isabel,
Santisteban Pilar,
Cerdán Sebastián
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.70062613.x
Subject(s) - phosphoenolpyruvate carboxykinase , ontogeny , enzyme , biology , cytosol , developmental profile , malic enzyme , biochemistry , isozyme , gene expression , endocrinology , gene , medicine , dehydrogenase
The ontogeny of the cerebral pyruvate recycling pathway and the cellular localization of associated enzymes, malic enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK), have been investigated using a combination of 13 C NMR spectroscopy, enzymatic analysis, and molecular biology approaches. Activity of the pathway, using [1,2‐ 13 C 2 ]acetate as a substrate, was detected by 13 C NMR in brain extracts 3 weeks after birth, increasing progressively up to the third month of age. In whole‐brain homogenates, ME activity increased to adult levels with the same time course as the recycling pathway. PEPCK activity was low during the first 2 weeks of life and decreased further toward adulthood. ME and PEPCK activity were found in primary cultures of astrocytes and in synaptosomal fractions of adult brain. Primary cultures of cortical neurons showed PEPCK activity but no detectable ME activity. The cytosolic ME gene was expressed in primary cultures of neurons and in astrocytes as well as in the neonatal and adult brain. The PEPCK gene was expressed both in primary cultures of cortical neurons and in astrocytes, but the level of its expression in the neonatal and adult brain was undetectable.