Abstract
A marine unicellular alga Emiliania huxleyi(Haptophyta) is the most abundant coccolithophorid. The alga gives the great impact on the global carbon cycle by blooms and the biological pump. Such activities should be supported by its photosynthetic activity. In this study we focused on the metabolism of glycolate, the product of Rubisco oxygenase reaction, since our previous study showed that the algal photosynthesis is sensitive to oxygen.
A homologous sequence of glycolate dehydrogenase (GDH) was found by sequence analysis of the E. huxleyi EST database. Northern blot analysis revealed that GDH mRNA level increased under light condition, but not dark condition. Main metabolites of 14C-glycolate were Glu and Gln. From the results, we concluded that GDH functions as a glycolate oxidizing enzyme to produce glyoxylate and then the compound is metabolized to Glu and Gln in E. huxleyi via a unique pathway that is different from the known glycolate pathway.
