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Titolo:
Kinetic studies on mitochondrial F-1-ATPase from crayfish (Orconectes virilis) gills
Autore:
Li, ZQ; Neufield, GJ;
Indirizzi:
Emporia State Univ, Dept Sci Biol, Emporia, KS 66801 USA Emporia State Univ Emporia KS USA 66801 t Sci Biol, Emporia, KS 66801 USA
Titolo Testata:
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY
fascicolo: 2, volume: 128, anno: 2001,
pagine: 339 - 350
SICI:
1096-4959(200102)128:2<339:KSOMFF>2.0.ZU;2-0
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEOTIDE-BINDING-SITES; ESCHERICHIA-COLI F1-ATPASE; PROTON ADENOSINE-TRIPHOSPHATASE; BEEF-HEART F1-ATPASE; NONCATALYTIC SITES; ATP SYNTHASE; ALPHA(3)BETA(3)GAMMA COMPLEX; OXIDATIVE-PHOSPHORYLATION; CATALYTIC SITES; SLOW BINDING;
Keywords:
crayfish; gills; mitochondria; F-1-ATPase; catalytic site; non-catalytic site; enzyme kinetics; ATP synthase;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
43
Recensione:
Indirizzi per estratti:
Indirizzo: Neufield, GJ Emporia State Univ, Dept Sci Biol, Emporia, KS 66801 USA Emporia State Univ Emporia KS USA 66801 mporia, KS 66801 USA
Citazione:
Z.Q. Li e G.J. Neufield, "Kinetic studies on mitochondrial F-1-ATPase from crayfish (Orconectes virilis) gills", COMP BIOC B, 128(2), 2001, pp. 339-350

Abstract

The substrate kinetics and the role of free Mg2+ and free ATP were studiedin membrane-bound F-1-ATPase from crayfish (Orconectes virilis) gills. It was shown that the MgATP complex was the true substrate for the ATPase activity with a K-m value of 0.327 mM. In the absence of bicarbonate, the maximum azide-sensitive activities in the presence and absence (<18 <mu>M) of free ATP were 0.878 and 0.520 mu mol P-i/mg protein/min, respectively, while the maximum bicarbonate-stimulated activity in absence of free ATP was 1.486 mu mol Pi/mg protein/min. Free ATP was a competitive inhibitor (K-i = 0.77 mM) and free Mg2+ was a mixed inhibitor (K-i = 0.81 mM, K-i' = 5.89 mM). However, free ATP also acted as an activator. Lineweaver-Burk plots for MgATP hydrolysis at high free Mg2+ concentrations exhibited an apparent negative cooperativity, which was not the case for high free ATP levels. These results suggest that, although free ATP inhibited the enzyme by binding to catalytic sites, it stimulated ATPase activity by binding to non-catalytic sites and promoted dissociation of inhibitory MgADP from the catalytic site. (C) 2001 Elsevier Science Inc All rights reserved.

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Documento generato il 20/01/20 alle ore 22:23:38