DELTA-AMINOLEVULINIC-ACID SYNTHASE FROM EUGLENA-GRACILIS

.delta.-Aminolevulinic acid (ALA) synthase [succinyl-CoA:glycine C-succinyltransferase (decarboxylating), EC 2.3.1.37] activity was detected in cell extracts of the unicellular green flagellate alga E. gracilis. The enzyme was identified by substrate and cofactor requirements and activity was proportional to number of cells extracted and duration of incubation. The incubation product was spectrophotmetrically and chromatographically identical to ALA. ALA synthase activity is present in strain 2 and E. gracilis var. bacillaris, and in nongreening, aplastidic strains derived from them. When grown in the dark, wild-type stains have amounts of ALA synthase activity equal to the amounts in their aplastidic derivative strains. Growth in the light or dark does not affect the level of ALA synthase activity in the aplastidic strains but the wild-type strains have only 1/3 as much activity when grown in the light. ALA synthase apparently is responsible for nonplastid tetrapyrrole biosynthesis in Euglena.