Mechanism of control by a circadian oscillator of chloroplast NADP-linked glyceraldehyde 3-phosphate dehydrogenase in Lemna gibba G3
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The mechanism controlling diurnal change in apparent Km for NADP of Chl-NADP-GPD of Lemna gibba G3 in continuous light was studied. This enzyme included two molecular species (Chl-NADP-GPD I and II) which were both bifunctional, i.e., NADP- and NAD-linked. Apparently, Chl-NADP-GPD I was an allosteric enzyme with a molecular weight of ca. 520,000 and a low affinity for NADP, whereas Chl-NADP-GPD II was a non-allosteric enzyme with a molecular weight of ca. 170,000 and a high affinity for NADP. In vitro. Chl-NADP-GPD I was dissociated to Chl-NADP-GPD II and a yet unidentified binding factor upon addition of DTT, ATP or NADP(H), while in their absence, Chl-NADP-GPD II associated with the binding factor to form Chl-NADP-GPD I. On the other hand, Vmax for NADP of Chl-NADP-GPD I (or II) in vivo decreased (or increased) in the subjective day phase of a day and increased (or decreased) in the subjective night phase. It was concluded that the decrease in Km of Chl-NADP-GPD in L. gibba G3 in the subjective day (4) could be ascribed to the promoted dissociation of Chl-NADP-GPD I due to an increased level of some DTT-like compound(s) and/or NADP(H), or to a decrease of NAD(H) and!or the binding factor, and that the increase in Km in the subjective night (4) could be ascribed to promoted association of Chl-NADP-GPD II with the binding factor due to a decrease in the amount of DTT-like compound(s) and/or NADP(H), or to an increase in NAD(H) and/or the binding factor.
- 日本植物生理学会の論文
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関連論文
- Modes of control by the circadian oscillator and the hourglass mechanism of the activities of cytoplasmic and chloroplast glyceraldehyde 3-phosphate dehydrogenases in Lemna gibba G3
- Mutually inverse rhythmic and sigmoidal changes in activity of cytoplasmic and chloroplast glyceraldehyde 3-phosphate dehydrogenases in Lemna gibba G3
- Mechanism of control by a circadian oscillator of chloroplast NADP-linked glyceraldehyde 3-phosphate dehydrogenase in Lemna gibba G3