Malate and Dihydroxyacetone Phosphate-dependent Nitrate Reduction in Spinach Leaf Protoplasts | Zendy

C.K.M. Rathnam | Zendy

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Malate and Dihydroxyacetone Phosphate-dependent Nitrate Reduction in Spinach Leaf Protoplasts

Author(s) -

C.K.M. Rathnam

Publication year - 1978

Publication title -

plant physiology

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 3.554

H-Index - 312

eISSN - 1532-2548

pISSN - 0032-0889

DOI - 10.1104/pp.62.2.220

Subject(s) - dihydroxyacetone phosphate , dhap , spinach , spinacia , nitrate , dihydroxyacetone , biochemistry , glyceric acid , phosphate , biology , chloroplast , chemistry , enzyme , organic chemistry , gene , glycerol , catalysis

Isolated spinach (Spinacia oleracea L. var. Bloomsdale) leaf protoplasts reduced nitrate at rates of 9 micromoles per milligram chlorophyll per hour in light with a 3- to 4-fold stimulation in the presence of HCO(3) (-). A similar stimulation of nitrate reduction in the absence of CO(2) fixation was obtained by the addition of malate, oxaloacetate (OAA), phospho-3-glyceric acid (PGA), or dihydroxyacetone phosphate (DHAP). Stimulation by malate and DHAP was light-independent, while the PGA and OAA effect was light-dependent. Nitrate reduction was found to be coupled to the cytoplasmic oxidation of DHAP or malate. The PGA/DHAP and OAA/malate shuttle across the chloroplast envelope has been demonstrated to support CO(2) fixation and/or nitrate reduction. The leaf protoplasts readily assimilated nitrate into amino-N in a stoichiometric relationship.

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