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Titolo:
Regulation of human glutamate dehydrogenases: Implications for glutamate, ammonia and energy metabolism in brain
Autore:
Plaitakis, A; Zaganas, I;
Indirizzi:
Univ Crete, Sch Hlth Sci, Sect Med, Dept Neurol, Iraklion, Crete, Greece Univ Crete Iraklion Crete Greece d, Dept Neurol, Iraklion, Crete, Greece
Titolo Testata:
JOURNAL OF NEUROSCIENCE RESEARCH
fascicolo: 5, volume: 66, anno: 2001,
pagine: 899 - 908
SICI:
0360-4012(200112)66:5<899:ROHGDI>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
AMINO-ACID SEQUENCE; GENE FAMILY; SPINOCEREBELLAR DEGENERATION; OLIVOPONTOCEREBELLAR ATROPHY; NEUROLOGICAL DISORDERS; EXOGENOUS GLUTAMATE; EXPRESSION ANALYSIS; ASTROCYTE CULTURES; MOLECULAR-CLONING; INSULIN RELEASE;
Keywords:
glutamate dehydrogenase; recombinant; L-leucine; ADP; GTP;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
66
Recensione:
Indirizzi per estratti:
Indirizzo: Plaitakis, A Univ Crete, Sch Hlth Sci, Sect Med, Dept Neurol, Iraklion, Crete, Greece Univ Crete Iraklion Crete Greece l, Iraklion, Crete, Greece
Citazione:
A. Plaitakis e I. Zaganas, "Regulation of human glutamate dehydrogenases: Implications for glutamate, ammonia and energy metabolism in brain", J NEUROSC R, 66(5), 2001, pp. 899-908

Abstract

Glutamate dehydrogenase (GDH) catalyzes the oxidative deamination of glutamate to alpha -ketoglutarate using NAD or NADP as cofactors. In mammalian brain, GDH is located predominantly in astrocytes, where it is probably involved in the metabolism of transmitter glutamate. The exact mechanisms that regulate glutamate fluxes through this pathway, however, have not been fully understood. In the human, GDH exists in heat-resistant and heat-labile isoforms, encoded by the GLUD1 (housekeeping) and GLUD2 (nerve tissue-specific) genes, respectively. These forms differ in their catalytic and allosteric properties. Kinetic studies showed that the Km value for glutamate for the nerve tissue GDH is within the range of glutamate levels in astrocytes (2.43 mM), whereas for the housekeeping enzyme, this value is significantly higher (7.64 mM; P < 0.01). The allosteric activators ADP (0.1-1.0 mM) and L-leucine (1.0-10.0 mM) induce a concentration-dependent enzyme stimulation that is proportionally greater for the nerve tissue-specific GDH (up to 1,600%) than for the housekeeping enzyme (up to 150%). When used together at lower concentrations, ADP (10-50 mM) and L-leucine (75-200 muM) act synergistically in stimulating GDH activity. GTP exerts a powerful inhibitory effect (IC50 = 0.20 mM) on the housekeeping GDH; in contrast, the nerve tissue isoenzyme is resistant to GTP inhibition. Thus, although the housekeeping GDH is regulated primarily by GTP, the nerve tissue GDH activity depends largely on available ADP or L-leucine levels. Conditions associated with enhanced hydrolysis of ATP to ADP (e.g., intense glutamatergic transmission) are likely to activate nerve tissue-specific GDH leading to an increased glutamate flux through this pathway. (C) 2001 Wiley-Liss, Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 23/01/20 alle ore 12:22:43