Changes in Plastidic and Cytoplasmic Pyruvate Kinase Activity during Chloroplast Development of Pea in Blue and Red Light

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Pyruvate kinase (PK) activity was demonstrated in the cytosol as well as in the plastids of pea leaves. Etioplasts and chloroplasts contained about 12% of the total activity. The presence of PK activity in different cellular compartments and the pronounced differences in kinetic and regulatory properties indicate that these activities are due to isoenzymes. When etiolated pea leaves were illuminated with weak blue light the plastidic PK activity increased immediately, reaching a maximum (about 21% of the total activity) after 24 h of illumination. Under red light, there was a lag period of about 4 h before the increase in isoenzyme activity. After 24 h of illumination, however, it reached the maximum found with blue light. In contrast, light quality had no appreciable effect on cytoplasmic PK and phosphoenolpyruvate carboxylase. Increases in NADP-dependent glyceraldehyde 3-phosphate dehydrogenase activity and in the soluble protein in the plastids were somewhat higher, whereas the increase in chlorophyll content was slightly lower under blue light than under red light. Blue light specifically increased the chlorophyll a/b-ratio. These different responses to the light quality during chloroplast development indicate that more than one photoreceptor is involved in these processes. The results obtained for pea PK also are discussed in comparison with similar findings for the chlorophyll-free Chlorella mutant no. 20.
日本植物生理学会の論文