Adrenergic-cyclic AMP regulation of biopterin biosynthesis in the pineal gland

Abstract

Tetrahydrobiopterin (6-(L-erythro-l’,2’-dihydroxypropyl)-2-amino-4-hydroxy-5,6,7,8-tetrahydropteridine) is a naturally occurring reducing agent; the only well established role for this compound is as a cofactor in the enzymatic hydroxylation of aromatic amino acids by a family of pterin-dependent mixed-function monooxygenases (Kaufman, 1974). This type of hydroxylation reaction is especially important in neurobiology because it is the intial step in the synthesis of the neurotransmitters dopamine, norepinephrine, and epinephrine from tyrosine and of serotonin from tryptophan. Recently there has been speculation and some evidence has been presented indicating that tetrahydrobiopterin might serve another role in neuroendocrine tissue, especially the pineal gland (Van der Have-Kirchberg et al., 1977). In this case, the concentration of tetrahydrobiopterin is 10 to 300-fold higher than in other tissues, and the ratio of tetrahydrobiopterin content to pterin-dependent hydroxylase activity is exceedingly high (Levine et al., 1979).