Inhibitory properties of nerve-specific human glutamate dehydrogenase isozyme by chloroquine.
Human glutamate dehydrogenase exists in hGDH1 (housekeeping isozyme) and in hGDH2 (nerve-specific isozyme), which differ markedly in their allosteric regulation. In the nervous system, GDH is enriched in astrocytes and is important for recycling glutamate, a major excitatory neurotransmitter during neurotransmission. Chloroquine has been known to be a potent inhibitor of house-keeping GDH1 in permeabilized liver and kidney-cortex of rabbit. However, the effects of chloroquine on nerve-specific GDH2 have not been reported yet. In the present study, we have investigated the effects of chloroquine on hGDH2 at various conditions and showed that chloroquine could inhibit the activity of hGDH2 at dose-dependent manner. Studies of the chloroquine inhibition on enzyme activity revealed that hGDH2 was relatively less sensitive to chloroquine inhibition than house-keeping hGDH1. Incubation of hGDH2 was uncompetitive with respect of NADH and non-competitive with respect of 2-oxoglutarate. The inhibitory effect of chloroquine on hGDH2 was abolished, although in part, by the presence of ADP and L-leucine, whereas GTP did not change the sensitivity to chloroquine inhibition. Our results show a possibility that chloroquine may be used in regulating GDH activity and subsequently glutamate concentration in the central nervous system.
Department of Biomedical Laboratory Science, Konyang University, Daejeon 320-718, Korea.
Myung-Min
MM
Choi
Eun-A
EA
Kim
Soo Young
SY
Choi
Tae Ue
TU
Kim
Sung-Woo
SW
Cho
Seung-Ju
SJ
Yang
D000494:Allosteric Regulation; D002490:Central Nervous System / Q000187:drug effects / Q000201:enzymology; D002738:Chloroquine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D005969:Glutamate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics; D007700:Kinetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D012559:Schizophrenia / Q000188:drug therapy / Q000201:enzymology
D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; D002738:Chloroquine; D005969:Glutamate Dehydrogenase; C061421:glutamate dehydrogenase (NAD(P)+)