The newborn screening for phenylketonuria (PKU) has become a common practice in many countries. The success of this type of mass screening is the result of the reliability of the Guthrie test in the identification of high blood phenylalanine levels. Recently, new syndromes other than PKU have been recognized that give high blood phenylalanine levels. These syndromes are referred to as “atypical...

In the protozoan parasite Leishmania, drug resistance can be a complex phenomenon. Several metabolic pathways and membrane transporters are implicated in the resistance phenotype. To monitor the expression of these genes, we generated custom DNA microarrays with PCR fragments corresponding to 44 genes involved with drug resistance. Transcript profiling of arsenite and antimony resistant mutants...

The enzymatic conversion of phenylalanine to tyrosine requires a reduced pteridine cofactor (1, 2). This requirement can be met by a naturally occurring compound with structure closely related to biopterin and sepia pteridine (3) or by certain synthetic pteridines such as 2-amino-4-hydroxy-6,7-dimethyl5,6,7 ,%tetrahydropteridine (4). In the presence of the latter compound, the hydroxylation rea...

The phenotypes of single- (SKO) and double-knockout (DKO) lines of dihydrofolate reductase-thymidylate synthase (DHFR-TS) of bloodstream Trypanosoma brucei were evaluated in vitro and in vivo. Growth of SKO in vitro is identical to wild-type (WT) cells, whereas DKO has an absolute requirement for thymidine. Removal of thymidine from the medium triggers growth arrest in S phase, associated with ...

R67 dihydrofolate reductase (DHFR) is a novel enzyme that confers resistance to the antibiotic trimethoprim. The crystal structure of R67 DHFR displays a toroidal structure with a central active-site pore. This homotetrameric protein exhibits 222 symmetry, with only a few residues from each chain contributing to the active site, so related sites must be used to bind both substrate (dihydrofolat...

Development of new antimycobacterial agents for Mycobacterium avium complex (MAC) infections is important particularly for persons coinfected with human immunodeficiency virus. The objectives of this study were to evaluate the in vitro activity of 2, 4-diamino-5-methyl-5-deazapteridines (DMDPs) against MAC and to assess their activities against MAC dihydrofolate reductase recombinant enzyme (rD...

Gene knockout and knockdown methods were used to examine essentiality of pteridine reductase (PTR1) in pterin metabolism in the African trypanosome. Attempts to generate PTR1 null mutants in bloodstream form Trypanosoma brucei proved unsuccessful; despite integration of drug selectable markers at the target locus, the gene for PTR1 was either retained at the same locus or elsewhere in the genom...

The enzymatic synthesis of dihydropteroate or dihydrofolate from 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine and p-aminobenaoate or p-aminobenzoylglutamate by bacterial extracts has been shown to require adenosine triphosphate (I-3). It has been postulated that a phosphorylated pteridine intermediate is involved before synthesis of folate-like compounds. Jaenicke and Chan (4) reported tha...