6-Acetyldihydrohomopterin and sepiapterin affect some GTP cyclohydrolase I's and not others

The first enzyme in pteridine biosynthesis, GTP cyclohydrolase I, is a likely site for regulation of pteridine biosynthesis to occur. GTP cyclohydrolase I responds to hormonal treatment and is found altered in a variety of mice with genetically based neurological and immunological disorders. Genetic loci can greatly modify the activity of GTP cyclohydrolase: Punch mutant in Drosophila hph-1 in mouse and atypical phenylketonuria in human. This report examines the ability of Ahp and sepiapterin to alter the activity of GTP cyclohydrolase I from mouse liver, rat liver and Drosophila head. 20 refs., 2 tabs