Abstract
The activities of nitrogen-assimilating enzymes in the marine macroalga, Bryopsis maxima Okamura ex Segawa (Chlorophyta) were studied. Changes in these enzymatic activities were observed during cultivation in a laboratory setting, and after the addition of chemicals. The following results were obtained. (1) The chloroplastic NADP-glutamate dehydrogenase (NADP-GDH; EC 1.4.1.4) increased by 49%, while the cytosolic/mitochondrial NADP-GDH decreased to 23% of its original level, showing organelle-specificity. Chloroplastic and cytosolic glutamine synthetases (GS; EC 6.3.1.2) showed 46% increases in 3 days, followed by decreases to their original levels. Chloroplastic NADPH-glutamate synthase (NADPH-GOGAT; EC 1.4.1.13) showed an increase. Cytosolic NADH-nitrate reductase (NADH-NR; EC 1.6.6.1) decreased to about half its original level in 7 days. (2) A compensatory enhancement of NADP-GDH activity was not observed when the GS activity was completely inhibited by methionine sulfoximine. (3) The chloroplastic NADP-GDH decreased to 82% while cytosolic/mitochondrial NADP-GDH increased to 250% with ATP treatment. These results suggest that the activities of nitrogen-assimilating enzymes are regulated independently in this alga.
Published Version
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