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Titolo:
The metabolic implications of intracellular circulation
Autore:
Hochachka, PW;
Indirizzi:
Univ British Columbia, Dept Zool, Vancouver, BC V6T 1Z4, Canada Univ British Columbia Vancouver BC Canada V6T 1Z4 ver, BC V6T 1Z4, Canada Univ British Columbia, Dept Radiol, Vancouver, BC V6T 1Z4, Canada Univ British Columbia Vancouver BC Canada V6T 1Z4 ver, BC V6T 1Z4, Canada Univ British Columbia, Sports Med Div, Vancouver, BC V6T 1Z4, Canada Univ British Columbia Vancouver BC Canada V6T 1Z4 ver, BC V6T 1Z4, Canada
Titolo Testata:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
fascicolo: 22, volume: 96, anno: 1999,
pagine: 12233 - 12239
SICI:
0027-8424(19991026)96:22<12233:TMIOIC>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENZYMATIC FLUX CAPACITIES; ATP TURNOVER RATES; SIGNAL-TRANSDUCTION; FLIGHT-MUSCLE; MAGNETIC-RESONANCE; CELL; GLYCOLYSIS; HOMEOSTASIS; MOVEMENT; PATHWAY;
Keywords:
metabolic regulation; oxygen delivery; oxygen regulation; intracellular perfusion; intracellular diffusion;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
71
Recensione:
Indirizzi per estratti:
Indirizzo: Hochachka, PW Univ British Columbia, Dept Zool, 6270 Univ Blvd, Vancouver,BC V6T 1Z4, Canada Univ British Columbia 6270 Univ Blvd Vancouver BC Canada V6T 1Z4
Citazione:
P.W. Hochachka, "The metabolic implications of intracellular circulation", P NAS US, 96(22), 1999, pp. 12233-12239

Abstract

Two views currently dominate research into cell function and regulation. Model I assumes that cell behavior is quite similar to that expected for a watery bag of enzymes and ligands. Model II assumes that three-dimensional order and structure constrain and determine metabolite behavior. A major problem in cell metabolism is determining why essentially all metabolite concentrations are remarkably stable (are homeostatic) over large changes in pathway fluxes-for convenience, this is termed the [s] stability paradox. For muscle cells, ATP and O-2 are the most perfectly homeostatic, even though O-2 delivery and metabolic rate correlate in a 1:1 fashion. In total, more than 60 metabolites are known to be remarkably homeostatic in differing metabolic states. Several explanations of [s] stability are usually given by traditional model I studies-none of which apply to all enzymes in a pathway, and all of which require diffusion as the means for changing enzyme-substrate encounter rates. In contrast, recent developments in our understanding of intracellular myosin, kinesin, and dyenin motors running on actin and tubulin tracks or cables supply a mechanistic basis for regulated intracellular circulation systems with cytoplasmic streaming rates varying over an approximately 80-fold range (from 1 to >80 mu m x sec(-1)). These new studies raise a model II hypothesis of intracellular perfusion or convection as a primary means for bringing enzymes and substrates together under variable metabolic conditions. In this view, change in intracellular perfusion rates cause change in enzyme-substrate encounter rates and thus change in pathway fluxes with no requirement for large simultaneous changes in substrate concentrations. The ease with which this hypothesis explains the [s] stability paradox is one of its most compelling features.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 22/09/20 alle ore 06:37:08