Giordano 2003 Plant Physiol

Giordano M, Norici A, Forssen M, Eriksson M, Raven JA (2003) An anaplerotic role for mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii. Plant Physiol 132:2126-34.

» PMID:12913167

Giordano Mario, Norici Alessandra, Forssen Magnus, Eriksson Mats, Raven John A (2003) Plant Physiol

Abstract: Previous studies of the mitochondrial carbonic anhydrase (mtCA) of Chlamydomonas reinhardtii showed that expression of the two genes encoding this enzyme activity required photosynthetically active radiation and a low CO₂ concentration. These studies suggested that the mtCA was involved in the inorganic carbon-concentrating mechanism. We have now shown that the expression of the mtCA at low CO(2) concentrations decreases when the external NH₄⁺ concentration decreases, to the point of being undetectable when NH₄⁺ supply restricts the rate of photoautotrophic growth. The expression of mtCA can also be induced at supra-atmospheric partial pressure of CO₂ by increasing the NH₄⁺ concentration in the growth medium. Conditions that favor mtCA expression usually also stimulate anaplerosis. We therefore propose that the mtCA is involved in supplying HCO₃^- for anaplerotic assimilation catalyzed by phosphoenolpyruvate carboxylase, which provides C skeletons for N assimilation under some circumstances.

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Algae, Photosynthesis