Effect of Temperature and External pH on the Cytoplasmic pH of<i>Chara corallina</i>

Raven, J. A.; Smith, Frank A.

doi:10.1093/jxb/29.4.853

Cited by 55 publications

(27 citation statements)

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“…This would maintain the H + /OH − ratio of water constant, and a constant ionization state of histidine residues which have a pK a1 that is close to cytoplasmic pH values. While many data on poikilothermic animals agree with the α-stat hypothesis, other data do not [10], and the only datum available for photosynthetic cells (giant cells of the green alga Chara corallina) shows that the change in cytoplasmic pH with temperature is less than that required by the α-stat hypothesis, but maintains approximate constancy of the cytoplasmic ratio of CO 2 /HCO 3 − with changing temperature [9]. While more data for photosynthetic cells, and especially for cyanobacteria, are needed, the datum available suggests that the CO 2 /HCO 3 − ratio is temperature-independent and that there is no superiority, on this basis, of sensing CO 2 rather than HCO 3 − .…”

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confidence: 95%

“…Calculation of the equilibrium ratio of CO 2 /HCO 3 − in the carboxysomes requires knowledge of the local pH, the temperature and the ionic strength [9]. Estimation of the intracellular (cytosolic) pH of cyanobacteria, determined by weak anion distribution or by NMR, does not refer directly to the contents of the carboxysome.…”

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confidence: 99%

“…Temperature is a determinant of pK a1 [9], and temperature variations on a diel basis are significant in some cyanobacterial environments, especially cyanobacterial mats in shallow waters [4]. Higher temperatures during the middle of the day decrease pK a1 and thus, for a given intracellular pH, decrease the CO 2 /HCO 3 − ratio [1,2].…”

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confidence: 99%

“…There is also a temperature effect on the regulated cytosolic pH of organisms, another determinant of the equilibrium CO 2 /HCO 3 − ratio at a given pK a1 [9]. The α-stat hypothesis for regulation of cytosolic pH with variations in temperature involves an increase in pH with decreasing temperature of some 0.016 pH units per degree Celsius of temperature decrease [9,10].…”

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confidence: 99%

“…The α-stat hypothesis for regulation of cytosolic pH with variations in temperature involves an increase in pH with decreasing temperature of some 0.016 pH units per degree Celsius of temperature decrease [9,10]. This would maintain the H + /OH − ratio of water constant, and a constant ionization state of histidine residues which have a pK a1 that is close to cytoplasmic pH values.…”

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Sensing inorganic carbon: CO2 and HCO3−

Raven

2006

Biochemical Journal

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Enzymes and transporters that catalyse reactions involving inorganic carbon are well characterized with respect to the species of inorganic carbon (CO 2 or HCO 3 − ) with which they interact. There is less information on the species recognized by proteins that sense inorganic carbon. In this issue of the Biochemical Journal, Hammer and colleagues show conclusively that cyanobacterial adenylyl cyclases are activated by CO 2 and not HCO 3 − , as was believed previously. While in some circumstances a similar in vivo regulatory outcome is achieved from sensing HCO 3 − as from sensing CO 2 , there are cases in which the outcomes are significantly different. The most striking example is where a compartment lacks carbonic anhydrase yet supports large metabolic fluxes of inorganic carbon species so that CO 2 and HCO 3 − are not at equilibrium. Other examples involve changes in pH, or temperature, of a compartment containing an equilibrium mixture of CO 2 and HCO 3 − .

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