Kinetic characterization of GABA-transaminase from cultured neurons and astrocytes.
The enzymatic mechanism and the kinetic parameters of GABA-transaminase extracted from cultured mouse cerebral cortex neurons and astrocytes were studied. Neuronal as well as astrocytic GABA-transaminase obeyed a bi bi ping-pong reaction mechanism. The estimated Km-values for alpha-ketoglutarate and GABA were significantly lower for astroglial GABA-transaminase compared to the neuronal enzyme suggesting a possible existence of cell specific isozymes of GABA-transaminase. The observed enzymatic mechanism and the magnitude of the estimated kinetic parameters imply that GABA-transaminase synthesized in the two types of cultured neural cells is mechanistically and kinetically equivalent to the enzyme synthesized in the brain in vivo.
Larsson
O M
OM
Department of Biological Sciences, Royal Danish School of Pharmacy, Copenhagen.
Schousboe
A
A
D000612:4-Aminobutyrate Transaminase / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000201:enzymology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000201:enzymology*; D007700:Kinetics; D051379:Mice; D009474:Neurons / Q000201:enzymology*
D000612:4-Aminobutyrate Transaminase