The  regulation of G6PDH has been studied in plants, eukaryotic algae and cyanobacteria, but the gene encoding G6PDH has been isolated from only a few of these sources. In plants, Glucose -6-phosphate dehydrogenase (G6PDH) is present in the cytosol and in plastids. High sugar levels in the cytosol results in higher enzyme levels and G6PDH activity. In contrast, plastidic G6PDH can be stimulated by low NADPH to NADP⁺ ratios and is restricted by reductive inactivation. Both isoforms are feedback inhibited by NADPH.