[The light-induced increase in the activity of NADP(+)-dependent glyceraldehyde-3-phosphate-dehydrogenase : VIII. The dependence of the enzyme activity in lemna on the intensity and the length of illumination].

1. A method for determination of the initial rate in enzymic non-linear progress reactions is described. 2. The relation between the increase in the activity of the NADP(+)-dependent glyceraldehyde-3-phosphate-dehydrogenase (GPD) and the different light intensities shows that Lemna gibba is adapted to high light intensities. 3. The time-curves for the increase in the activity of the enzyme in dependence on the different light intensities are similar to the corresponding curves for the intensity of photosynthesis. 4. The activity of the NAD(+)-dependent GPD in the extract decreases after preceding illumination of the plants; this activity is thus inverse to that of the NADP(+)-specific enzyme. There are indications (also in the literature) that the two enzymes are interconvertible.