The fine structure and the composition of pteridine pigments of erythrophores in adults of the swordtail fish, Xiphophorus helleri, were studied by means of cytochemistry, paper chromatography, ionophoresis, centrifugal fractionation, and electron microscopy. It was found that water-soluble pigments of erythrophores consisted exclusively of pteridine derivatives including large amounts of droso...

The antitumor compound PT523 [N(alpha)-(4-amino-4-deoxypteroyl)-N(delta)-hemiphthaloyl-L- ornithine] was found to have an inhibition constant (K(i)) of 0.35 +/- 0.10 pM against human dihydrofolate reductase (hDHFR), 15-fold lower than that of the classical antifolate drug methotrexate (MTX). The structure of PT523 bound to hDHFR and hDHFR-NADPH was investigated using multinuclear NMR techniques...

(Z)-Tetrahydropteroyltriglutamate and (Z)-tetrahydropteroylhexaglutamate were prepared and tested as substrates for thymidylate synthetase (EC 2.1.1.6) (methylenetetrahydrofolate: deoxyuridylate C-methyltransferase) from Zactobacillus casei. Both tetrahydropteroylpolyglutamates were more effective substrates than (Z)-tetrahydropteroylglutamate, enhancing the reaction rate 3-fold when compared a...

A progressive loss of photosynthetic activity occurred when cells of Anacystis nidulans and Coccochloris peniocystis were incubated in increasing concentrations of osmotica from 0.2 to 0.7 M, and there was a release of pteridine from the cells proportional to the loss of photosynthetic activity.

Nitric oxide (NO) is synthesised from L-arginine by the enzyme NO synthase (NOS). The complex reaction involves the transfer of electrons from NADPH, via the flavins FAD and FMN in the carboxy-terminal reductase domain, to the haem in the amino-terminal oxygenase domain, where the substrate L-arginine is oxidised to L-citrulline and NO. The haem is essential for dimerisation as well as NO produ...

Leishmaniasis is a growing health problem worldwide. As there are certain drawbacks with the drugs currently used to treat human leishmaniasis and resistance to these drugs is emerging, there is a need to develop novel antileishmanial compounds, among which isoquinoline alkaloids are promising candidates. In this study, 18 novel oxoisoaporphine derivatives were synthesized and their possible an...

The presence of a remarkably high concentration of pteridiineS in the blue green alga, Anacystis nidulanis 5, wvas demonstrated by Forrest, van Baalen, and Myers in 1957 (2). A number of (lifferent pteridines were then isolated and ideentifie(l. These included 2-amino-4-hydroxypteridine, 2,6-diamino-4-hydroxypteridline (10), a yellow pteridine assigned the structure 2-aimino-4-hydroxv-6-propion...