Die lichtinduzierte aktivitätssteigerung der NADP+-abhängigen glycerinaldehyd-3-phosphat dehydrogenase IV. Der einfluss auf die photosyntheseintensität

Abstract

1. 1. In Lemma gibba L. the reversible increase in the activity of NADP+-dependent glyceraldehyde-3-phosphate dehydrogenase by illumination is inhibited not only by chloramphenicol (cf. ref. 1) but also by amino acid analogues like dl-p-fluorophenyl-alanine (10−2, 10−3 M) and dl-ethionine (10−2 M). This block is removed to a great extent by equimolar concentrations of the corresponding amino acids (phenyl-alanine or methionine). 2. 2. In Lemma the same concentrations of the inhibitory substances strongly reduce the photosynthetic O2 production. The inhibition by the amino acid analogues is more pronounced at the commencement of the light phase and is then diminished, probably under the influence of the photosynthetically produced amino acids. This reduction of inhibition is also brought about by the addition of the corresponding amino acids via the medium. 3. 3. The possibilities for a relationship between the intensity of the photosynthesis and the increase in activity of the enzyme in the light are discussed, emphasizing a feed-back control of the photosynthetic capacity by light.