Effects of illumination of etiolated leaves on the redox state of NADP in the plastids

Mapleston, R.E.; Griffiths, W. T.

doi:10.1016/0014-5793(78)80746-7

Cited by 19 publications

(12 citation statements)

References 12 publications

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“…1), and after 2 h, only about 25% of the activity remains. This observation is very reminiscent of the behavior of the enzyme in whole leaves under similar conditions (17)(18)(19).…”

Section: Methodsmentioning

confidence: 68%

“…It has also been observed that such in vivo illumination simultaneously caused oxidation of the plastid NADPH and a decrease in Pchlide level as a result of photoconversion. Redarkening of briefly illuminated plants produced an exact reversal ofthe situation with re-reduction of the plastid NADP and resynthesis of Pchlide accompanying recovery of Pchlide reductase activity (17)(18)(19). After identification ofthe enzyme protein (1,20), it became apparent that the observed changes in enzyme activity results from a degradation and resynthesis of the actual enzyme protein under conditions of illumination and redarkening.…”

mentioning

confidence: 99%

“…It has previously been demonstrated (17,18) that illumination of etiolated plants leads to a dramatic decrease in the activity of the plastid-localized enzyme Pchlide reductase. It has also been observed that such in vivo illumination simultaneously caused oxidation of the plastid NADPH and a decrease in Pchlide level as a result of photoconversion.…”

mentioning

confidence: 99%

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Light-Induced Breakdown of NADPH-Protochlorophyllide Oxidoreductase In Vitro

Kay¹,

Griffiths²

1983

Plant Physiol.

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Light-induced loss of the enzyme protochlorophylide reductase (EC 1.6.99.1.), already described as a characteristic of whole plants, has now been demonstrated in vitro using etioplast membrane preparations ofAvexa Sativa L. var Peniarth and Secal cerealk L. var RheidoL Some evidence is presented, based upon temperature, pH, and inhibitor sensitivity of the process, that loss of enzyme may be the result of proteolysis. The lghtinduced process can, in vitro, be largely prevented by addition of the substrates of the reductase, protochlorophyflide and NADPH. It is concluded that Ught causes the breakdown of the reductase in vivo and in vitro by producing ligand-free enzyme as a consequence of the photoconversion reaction.It has previously been demonstrated (17, 18) that illumination of etiolated plants leads to a dramatic decrease in the activity of the plastid-localized enzyme Pchlide reductase. It has also been observed that such in vivo illumination simultaneously caused oxidation of the plastid NADPH and a decrease in Pchlide level as a result of photoconversion. Redarkening of briefly illuminated plants produced an exact reversal ofthe situation with re-reduction of the plastid NADP and resynthesis of Pchlide accompanying recovery of Pchlide reductase activity (17-19). After identification ofthe enzyme protein (1,20), it became apparent that the observed changes in enzyme activity results from a degradation and resynthesis of the actual enzyme protein under conditions of illumination and redarkening. However, the mechanism whereby light produced this change is unexplained. Again, the significance, if any, of the accompanying changes in Pchlide and NADPH, in regulation ofthe level of Pchlide reductase, also remained obscure.In the present paper, the light-induced loss of Pchlide reductase has been mimicked by illumination of cell-free preparations in vitro. Further, and more significantly, the process is shown to be largely inhibited by addition of Pchlide and NADPH prior to illumination. From the data, a simple model to account for the light-induced loss of reductase activity is proposed. An account of this work has already been presented briefly at the Nato Advanced Study Institution on "Molecular models of photoresponsiveness",

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“…1), and after 2 h, only about 25% of the activity remains. This observation is very reminiscent of the behavior of the enzyme in whole leaves under similar conditions (17)(18)(19).…”

Section: Methodsmentioning

confidence: 68%

mentioning

confidence: 99%

See 1 more Smart Citation

Light-Induced Breakdown of NADPH-Protochlorophyllide Oxidoreductase In Vitro

Kay¹,

Griffiths²

1983

Plant Physiol.

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show abstract

“…2) In whole leaves the Chlide 678 form is rapidly transformed (Fig. 1) (20). The failure of holochrome preparations (1,14,23) and unsupplemented purified membranes (Fig.…”

Section: Effects Of Exogenous Nadp(h) On the Absorbance Of Chlidementioning

confidence: 97%

“…The interfacial material was subsequently removed, diluted with buffer II, and recentrifuged (22). Total membranes and sucrose-gradientpurified membranes were resuspended in buffer I (0.5 M sucrose, 20 mM Tes, 20 mM Hepes, 2 mM MgCI2, 1 mm EDTA, 5 mM cysteine, pH 7.5) and could be stored indefinitely at -20°C without significant loss of activity. All operations were performed in a cold room at 4°C under dim green illumination.…”

mentioning

confidence: 99%