Studies of Delta-Aminolevulinic Acid Dehydrase from Skeletonema costatum, a Marine Plankton Diatom

The accumulation of delta-aminolevulinic acid and activities of delta-aminolevulinic acid dehydrase were examined in the marine diatom, Skeletonema costatum, grown in the presence of levulinic acid. Levulinic acid concentrations greater than 10 mm affect growth and morphology, and inhibit chlorophyll synthesis. The algae recover from the effects of levulinic acid after 48 hours of exposure. The recovery is characterized by increased cellular cholorphyll content, decreased delta-aminolevulinic acid accumulation, decreased 3-(3,4-dichlorophenyl)-1, 1-dimethylurea-enhanced in vivo fluorescence, and the induction of a levulinic acid-activated delta-aminolevulinic acid dehydrase which does not follow Michaelis-Menten kinetics. The data indicate that levulinic acid blocks may be ineffective in vivo, and that delta-aminolevulinic acid is metabolized to amino and dicarboxylic acids. delta-Aminolevulinic acid dehydrase activities are used to estimate the capacity for chlorophyll synthesis. Results suggest this diatom may be capable of rapid chlorophyll turnover, which would allow the plant to light-shade adapt on the time scales appropriate to vertical mixing rates in the sea.