Glutamate Dehydrogenase in Human Brain: Regional Distribution and Properties

: Glutamate dehydrogenase (GDH) activity was studied in 17 regions of six human brains. Duration and conditions of the postmortem period did not affect enzyme activity. Specific activity ranged between 103 and 377 nmoles/min/mg protein at 25°C and it was 10‐fold higher than that found in leukocytes. Apart from exclusively white matter regions (corpus callosum and centrum ovale), there was a moderate regional distribution (2.5‐fold variation), with highest values in the inferior olive and hypothalamus, and lowest in the cerebellum and lenticular nucleus. With α‐ketoglutarate (α‐KG), NADH, or NH4+ as variable substrate, the apparent Km values in human brain were Kmα‐KG= 1.9 × 10−3 M, KmNADH= 0.21 × 10−3 M, and KmNH4+= 28 × 10−3 M, and in leukocytes they were Kmα‐KG= 1.7 × 10−3 M, KmNADH= 0.24 × 10−3 M, and KmNH4+= 28 × 10−3 M. The effects of cofactors, inhibitor, and pH were similar in brain and leukocyte GDH.