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Titolo:
Kinetics of rat brain and liver solubilized membrane-bound catechol-O-methyltransferase
Autore:
Bonifacio, MJ; Vieira-Coelho, MA; Borges, N; Soares-da-Silva, P;
Indirizzi:
BIAL, Dept Res & Dev, P-4745457 Sao Mamede Do Coronado, Portugal BIAL SaoMamede Do Coronado Portugal P-4745457 ede Do Coronado, Portugal Univ Porto, Fac Med, Inst Farmacol & Terapeut, P-4200 Porto, Portugal UnivPorto Porto Portugal P-4200 acol & Terapeut, P-4200 Porto, Portugal
Titolo Testata:
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
fascicolo: 2, volume: 384, anno: 2000,
pagine: 361 - 367
SICI:
0003-9861(200012)384:2<361:KORBAL>2.0.ZU;2-R
Fonte:
ISI
Lingua:
ENG
Soggetto:
TIGHT-BINDING INHIBITORS; RABBIT THORACIC AORTA; MESSENGER-RNAS; METHYLATION; PURIFICATION; EXPRESSION; RECEPTOR; ENZYME; FORMS; TOLCAPONE;
Keywords:
S-COMT; MB-COMT; Triton-X100 solubilization; liver; brain;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Soares-da-Silva, P BIAL, Dept Res & Dev, A Av Siderurgia Nacl, P-4745457 Sao Mamede Do Coronado, Portugal BIAL A Av Siderurgia Nacl Sao Mamede Do Coronado Portugal P-4745457
Citazione:
M.J. Bonifacio et al., "Kinetics of rat brain and liver solubilized membrane-bound catechol-O-methyltransferase", ARCH BIOCH, 384(2), 2000, pp. 361-367

Abstract

Catechol-O-methyltransferase (COMT), an enzyme involved in the metabolism of catecholamines, is present in mammals as soluble (S-COMT) and membrane-bound (MB-COMT) forms. The kinetic properties of rat liver and brain solubilized MB-COMT were evaluated and compared with the ones of the respective native enzymes. Treatment with Triton X-100 did not affect the affinity of S-COMT for the substrate (adrenaline) or the activity of the enzyme. Conversely, solubilized MB-COMT presented a lower affinity for the substrate than the native protein, as evidenced by a significant increase in the K-m values: 9.3 (6.2, 12) vs 2.5 (0.8, 4.3) muM for the liver enzyme and 12 (11, 13) vs 1.4 (1.0, 1.9) muM for the brain enzyme. A 1.6- and 1.5-fold increase inV-max was also observed for the liver and brain solubilized enzymes, respectively, The actual enzyme concentrations (molar equivalence, nil,,) and their efficiency in the O-methylation reaction (catalytic number, K-cat) weredetermined from Ackermann-Potter plots. Both liver and brain solubilized MB-COMT were more efficient in methylating adrenaline than the respective native enzymes as revealed by higher K-cat values (P < 0.05): 16.4 +/- 0.9 vs10.9 +/- 0.8 min(-1) (brain) and 5.9 +/- 0.3 vs 3.3 +/- 0.2 min(-1) (liver). Subjecting liver solubilized MB-COMT to further purification increased the K-m of the enzyme to the levels of liver S-COMT, 252 (127; 377) vs 257 (103; 411) <mu>M. The solubilization process significantly alters MB-COMT kinetic properties but only after partial purification does the enzyme present an affinity for the subtrate identical to S-COMT. (C) 2000 Academic Press.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 15/07/20 alle ore 13:55:25