[From butterflies to neurobiology and the diagnosis of AIDS. The 100th anniversary of the discovery of pteridines].

The first report on the isolation of pteridines from biological materials was published in 1889. During the last 100 years a large number of pteridines have been isolated from many different organisms and have been shown to be involved in several biochemical processes. The best characterized biologically occurring unconjugated pteridine, i.e. tetrahydrobiopterin, is a cofactor for amino acid hydroxylases, such as phenylalanine, tyrosine and tryptophan hydroxylase. The last two enzymes catalyze the rate-limiting steps in the synthesis of important biogenic amines, such as dopamine, noradrenaline, adrenaline and serotonin. Several inborn errors in the biosynthesis of tetrahydrobiopterin have provided more insight into variant forms of phenylketonuria (Følling's disease). Recently, it has been shown that pteridines also are involved in immunological responses, and neopterin has been suggested as a diagnostic marker for malignancies, virus infections and acute rejection episodes following allotransplantation.