Abstract
A highly specific dihydropterin deaminase was discovered in Drosophila melanogaster and was purified 60-fold over that of the crude extract. The enzyme specifically deaminates 7,8-dihydropterin forming the corresponding 7,8-dihydrolumazine. The enzyme does not deaminate the following compounds: pterin, xanthopterin, dihydroxanthopterin, sepiapterin, isosepiapterin, biopterin, dihydrobiopterin, neopterin, 6-hydroxymethylpterin, 6-methylpterin, 7-methylpterin, 6,7-dimethylpterin, pterin-6-carboxylic acid, isoxanthopterin, isoxanthopterin-6-carboxylic acid, 6-methylisoxanthopterin, 6-methyl-tetrahydropterin, drosopterin and isodrosopterin. The pH optimum of the enzymatic reaction is approximately 8.5 and the K m value is 1.3 mM. The molecular weight of the enzyme is 73,000 as estimated by gel filtration. The non-fluorescent product of the reaction, 7,8-dihydrolumazine, was non-enzymatically oxidized to blue fluorescent 6-hydroxylumazine.
