The Potential effect of Low Cell Osmolarity on Cell Function through decreased concentration of enzyme substrates

J. A. Raven (Lead / Corresponding author)

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    Abstract

    Some freshwater algae have lower (<130 osmol m-3) intracellular osmolarities than most others (>180 osmol m-3). Low osmolarities are related to the presence of flagella and the low energy cost of active water efflux following downhill water influx unconstrained by cell walls covering the plasmalemma, and the low resource cost of cell wall synthesis with the same mechanical degree of safety. One consequence of low intracellular osmolarity is limitation on the concentration of metabolites, that is, substrates and products of enzyme activity. Models of the flux through metabolic pathways, and hence the specific growth rate, using steady-state concentrations of enzymes and metabolites have involved organisms with intracellular metabolite osmolarities >280 osmol m-3, where the metabolite concentrations are much greater than the total osmolarity of some freshwater algae. Since the protein concentration (mol m-3) in the cells and the specific growth rates of freshwater cells with low and with higher intracellular osmolarity are highly similar, the models of trade-offs between enzyme and metabolite concentrations for cells with high intracellular osmolarity need modification for cells with low intracellular osmolarity. The soluble free-radical scavenger ascorbate can constitute as little as 0.2% of the low intracellular metabolite concentration (mol m-3) of low-intracellular-osmolarity cells.

    Original languageEnglish
    Pages (from-to)4667-4673
    Number of pages7
    JournalJournal of Experimental Botany
    Volume69
    Issue number20
    Early online date10 Jul 2018
    DOIs
    Publication statusPublished - 14 Sep 2018

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    Keywords

    • Active water transport
    • UV screens
    • ascorbate
    • enzyme concentration
    • metabolite concentration
    • osmolarity
    • trade-offs

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