Evidence for Photoreduction of NADP + in a Suspension of Lysed Plastids from Etiolated Bean Leaves

N A D P H , N A D P + Photoreduction, Etioplasts, Absorbance Difference Spectra, Phaseolus vulgaris It has been investigated if photoreduction of N A D P + (detected by absorption spectroscopy) may take place in lysed plastids within minutes of exposure to light. This process was made possible by removal of oxidants from the reaction mixture. Lysed plastids were suspended in a medium containing N A D P + , catalase, glucose oxidase and glucose; exposure to light simultaneously to addition of ferredoxin and ferredoxin-NADP reductase, resulted in increased absorbance in the band around 340 n m , while addition of 3-phosphoglycerate resulted in the disappearance of this band. Ferredoxin and ferredoxin-NADP reductase are only effective when photoactivation takes place before their addition to the medium.