CHARACTERIZATION OF SEPIAPTERIN REDUCTASE-ACTIVITY FROM DROSOPHILA-MELANOGASTER

A kinetic study of Drosophila melanogaster sepiapterin reductase has b een done. The apparent K-m for sepiapterin has been estimated as 153 m u M. N-acetyldopamine, N-acetylserotonin, and N-methoxyacetylserotonin have shown to be noncompetitive inhibitors for the Drosophila sepiapt erin reductase. The K-i obtained were 40 mu M, 127 mu M and 87 mu M, r espectively. Chromatofocusing of Drosophila crude extracts has shown o nly one peak with sepiapterin reductase activity, corresponding to pI 6.0. A study of the activity in different eye-color mutant strains rev ealed significantly decreased levels in clot, red Malpighian tubules a nd garnet.