observed in enzyme-methotrexate complexes. The orientation that appears to be required for catalysis can be readily achieved by rotations of the pteridine of 180° around the C-6-C-9 bond and 30° about the C-9-N-10 bond. In this orientation, C-4 of the NADPH nicotinamide ring closely approaches C-6 of the substrate, and N-5 of the substrate is adjacent to aspartic acid-30 of the enzyme. It has b...

The brown gene of Drosophila melanogaster is required for deposition of pteridine pigments in the compound eye and other tissues. We isolated a ca. 150-kilobase region including brown by microdissection and chromosome walking using cosmids. Among the cDNAs identified by hybridization to the cosmids, one class hybridized to a genomic region that is interrupted in two brown mutants, bw and In(2LR...

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 b...

In the title compound, [Co(C8H5N5O3)(C12H8N2)(H2O)]·3H2O, a tridentate 2-amino-7-methyl-4-oxidopteridine-6-carboxyl-ate ligand, a bidentate ancillary 1,10-phenanthroline (phen) ligand and a water mol-ecule complete a distorted octa-hedral geometry around the Co(II) atom. The pterin ligand forms two chelate rings. The phen and pterin ring systems are nearly perpendicular [dihedral angle = 85.15 ...

Influx of [3H]methotrexate into freshly isolated hepatocytes in suspension is mediated by two routes, one with a high affinity (Km = 5.9 microM) and another with a low affinity for methotrexate. Both transport routes are equally sensitive to the sulfhydryl group inhibitor, p-chloromercuriphenylsulfonic acid, alterations in temperature, substitution of extracellular Na+ with choline, and inhibit...

Folate, a water soluble B vitamin, is the generic term for both natural folylpolyglutamate derivatives (including methylfolate), and synthetic folic acid (pterolymonoglutamic acid, PteGlu). Folate consists of three molecular components; a pteridine ring, paraaminobenzoic acid and glutamic acid residues conjugated to the pteridine (Lucock, 2000). The natural form of folate found in food generall...

Catecholamines [dopamine, noradrenaline (norepinephrine), and adrenaline (epinephrine); CAs] are neurotransmitters in the central and peripheral nervous systems as well as hormones in the endocrine system. CAs in the brain play a central role in versatile functions as slow-acting neurotransmitters functioning in synaptic neurotransmission, modulating the effects of fast-acting neurotransmitters...

The metabolism of the methyl group of 5-methyltetrahydrofolate was studied in rats in which cobalamin had been inactivated by exposure to nitrous oxide and in air-breathing control animals. Methylfolate labeled with [14C] in the methyl group and with [3H] in the pteridine-PABA portion was injected and the disappearance of [14C]H3- relative to [3H]folate was measured in liver. The half-time of t...