Some aspects of pteridine biosynthesis in amphibians.

SOME ASPECTS OP PTERIDINE BIOSYNTHESIS IN AMPHIBIANS by Hamilton Lee Stackhouse Bright fluorescing unconjugated pteridines have been extracted from amphibians; yet the biological function of these compounds in vertebrates is not completely understood. There is some evidence, indicating that they can act as pigments, co-factors, and growthpromoting substances. Pteridine biosynthesis is unknown but it appears to have a parallel biosynthesis with the.purines. Rana catesbeiana larval integument will convert carbon-l^-labeled guanine to at least two pteridines: biopterin and 2-amino-U-hydroxypteridine-6-carboxylic acid. Intermedin will cause pteridine deposition and purine depletion in the dorsal integument of Rana pipiens and Rana sylvatica larvae. Thus, it seems probable that in amphibians the integumental pteridines may be synthesized from the purines. This study was designed to inves­ tigate the synthetic pathways of unconjugated pteridines in an in-vivo system. The hypophyseal placode was removed from early tail bud Rana sylvatica larvae. Normal and hypophysioprivic Rana sylvatica larvae were injected with glycine-(u.l. )-^C. Some of the hypophysioprivic larvae were injected with a hormone preparation containing large amounts of intermedin. Pteridines and purines were extracted from homogenized