title: Folate-synthesizing enzyme system as target for development of inhibitors and inhibitor combinations against Candida albicans-synthesis and biological activity of new 2,4-diaminopyrimidines and 4'-substituted 4-aminodiphenyl sulfones.
abstract: The paper describes the design, synthesis, and testing of inhibitors of folate-synthesizing enzymes and of whole cell cultures of Candida albicans. The target enzymes used were dihydropteroic acid synthase (SYN) and dihydrofolate reductase (DHFR). Several series of new 2,4-diaminopyrimidines were synthesized and tested as inhibitors of DHFR and compared with their activity against DHFR derived from mycobacteria and Escherichia coli. To test for selectivity, also rat DHFR was used. A series of substituted 4-aminodiphenyl sulfones was tested for inhibitory activity against SYN and the I(50) values compared to those obtained previously against Plasmodium berghei- and E. coli-derived SYN. Surprisingly, QSAR equations show very similar structural dependencies. To find an explanation for the large difference in the I(50) values observed for enzyme inhibition (SYN, DHFR) and for inhibition of cell cultures of Candida, mutant strains with overexpressed efflux pumps and strains in which such pumps are deleted were included in the study and the MICs compared. Efflux pumps were responsible for the low activity of some of the tested derivatives, others showed no increase in activity after pumps were knocked out. In this case it may be speculated that these derivatives are not able to enter the cells.
authors.affiliation: Division of Structural Biochemistry, Research Center Borstel, Leibniz Center for Medicine and Biosciences, Parkallee 1-40, D-23845 Borstel, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Otzen
authors.forename: Ellen G
authors.initials: EG
authors.lastname: Wempe
authors.forename: Brigitte
authors.initials: B
authors.lastname: Kunz
authors.forename: Rainer
authors.initials: R
authors.lastname: Bartels
authors.forename: Gudrun
authors.initials: G
authors.lastname: Lehwark-Yvetot
authors.forename: Wolfram
authors.initials: W
authors.lastname: Hänsel
authors.forename: Klaus-Jürgen
authors.initials: KJ
authors.lastname: Schaper
authors.forename: Joachim K
authors.initials: JK
authors.lastname: Seydel
mesh_terms: D000631:Aminopyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D000935:Antifungal Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D004094:Dihydropteroate Synthase / Q000737:chemistry / Q000378:metabolism; D004338:Drug Combinations; D026141:Drug Resistance, Multiple, Fungal; D005493:Folic Acid Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D021281:Quantitative Structure-Activity Relationship; D051381:Rats; D013450:Sulfones / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism
chemical_list: D000631:Aminopyridines; D000935:Antifungal Agents; D004338:Drug Combinations; D005493:Folic Acid Antagonists; D013450:Sulfones; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase