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Titolo:
Nerve tissue-specific (GLUD2) and housekeeping (GLUD1) human glutamate dehydrogenases are regulated by distinct allosteric mechanisms: Implications for biologic function
Autore:
Plaitakis, A; Metaxari, M; Shashidharan, P;
Indirizzi:
Univ Crete, Sch Hlth Sci, Med Sect, Dept Neurol, Heraklion, Crete, Greece Univ Crete Heraklion Crete Greece Dept Neurol, Heraklion, Crete, Greece CUNY Mt Sinai Sch Med, Dept Neurol, New York, NY 10029 USA CUNY Mt Sinai Sch Med New York NY USA 10029 eurol, New York, NY 10029 USA
Titolo Testata:
JOURNAL OF NEUROCHEMISTRY
fascicolo: 5, volume: 75, anno: 2000,
pagine: 1862 - 1869
SICI:
0022-3042(200011)75:5<1862:NT(AH(>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
RAT-BRAIN; SPINOCEREBELLAR DEGENERATION; ULTRASTRUCTURAL-LOCALIZATION; OLIVOPONTOCEREBELLAR ATROPHY; NEUROLOGICAL DISORDERS; EXOGENOUS GLUTAMATE; ASTROCYTE CULTURES; CEREBELLAR CORTEX; INSULIN RELEASE; AMINO-ACID;
Keywords:
glutamate dehydrogenase; L-leucine; ADP; GTP; GLUD1; GLUD2; allosteric regulation; baculovirus;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Plaitakis, A Univ Crete, Sch Hlth Sci, Med Sect, Dept Neurol, Heraklion, Crete, Greece Univ Crete Heraklion Crete Greece Heraklion, Crete, Greece
Citazione:
A. Plaitakis et al., "Nerve tissue-specific (GLUD2) and housekeeping (GLUD1) human glutamate dehydrogenases are regulated by distinct allosteric mechanisms: Implications for biologic function", J NEUROCHEM, 75(5), 2000, pp. 1862-1869

Abstract

Human glutamate dehydrogenase (GDH), an enzyme central to the metabolism of glutamate, is known to exist in housekeeping and nerve tissue-specific isoforms encoded by the GLUD1 and GLUD2 genes, respectively. As there is evidence that GDH function in vivo is regulated, and that regulatory mutations of human GDH are associated with metabolic abnormalities, we sought here tocharacterize further the functional properties of the two human isoenzymes. Each was obtained in recombinant form by expressing the corresponding cDNAs in Sf9 cells and studied with respect to its regulation by endogenous allosteric effecters, such as purine nucleotides and branched chain amino acids. Results showed that L-leucine, at 1.0 mM, enhanced the activity of the nerve tissue-specific (GLUD2-derived) enzyme by similar to 1,600% and that of the GLUD1-derived GDH by similar to 75%. Concentrations of L-leucine similar to those present in human tissues (similar to 0.1 mM) had little effect on either isoenzyme. However, the presence of ADP (10-50 mu M) sensitizedthe two isoenzymes to L-leucine, permitting substantial enzyme activation at physiologically relevant concentrations of this amino acid. NonactivatedGLUD1 GDH was markedly inhibited by GTP (IC50 = 0.20 mu M), whereas nonactivated GLUD2 GDH was totally insensitive to this compound (IC50 > 5,000 mu M). In contrast, GLUD2 GDH activated by ADP and/or L-leucine was amenable to this inhibition, although at substantially higher GTP concentrations thanthe GLUD1 enzyme. ADP and L-leucine, acting synergistically, modified the cooperativity curves of the two isoenzymes. Kinetic studies revealed significant differences in the K-m values obtained for or-ketoglutarate and glutamate for the GLUD1- and the GLUD2-derived GDH, with the allosteric activators differentially altering these values. Hence, the activity of the two human GDH is regulated by distinct allosteric mechanisms, and these findings may have implications for the biologic functions of these isoenzymes.

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Documento generato il 23/01/20 alle ore 06:29:57