Abstract
A pterin deaminase catalyzing the hydrolytic deamination of various pteridines was found in the bacterium, Bacillus megaterium, and partially purified from bacterial extract. The specific activity was raised 90-fold over that of the crude extract. The pH optimum is around 7.3, and the Km value for 6-carboxypterin is 1.3mM. The molecular weight of the enzyme was estimated by gel filtration to be about 110, 000. The enzyme deaminated pterin, 6-carboxy-pterin, biopterin, 6-methylpterin, 7-methylpterin, xanthopterin, 6-hydroxymethylpterin, sepiapterin, isosepiapterin, folic acid, and 6, 7-dimethylpterin to their corresponding lumazines, whereas guanine, 7-carboxypterin, leucopterin, isoxanthopterin, and 6-methylisoxanthopterin did not serve as substrates. The enzyme was inhibited by PCMB and 8-azaguanine.
