ABSTRACT
Oxythiamine (OT) and 3-deazathiamine (DAT) are the antimetabolites of thiamine. The aim of study was to compare the effects of OT and DAT pyrophosphates (-PP) on the kinetics of mammalian pyruvate dehydrogenase complex (PDHC) and the in vitro culture of HeLa cells. The kinetic study showed that 3-deazathiamine pyrophosphate (DATPP) was a much stronger competitive inhibitor (Ki = 0.0026 µM) of PDHC than OTPP (Ki = 0.025 µM). Both Ki values were much lower versus K m for thiamine pyrophosphate (0.06 µM). However, DATPP added to the culture medium for the HeLa cells culture did not hamper the rate of cell growth and showed not significant impact on the viability of the cells, whereas OTPP and OT showed a significant cytostatic effect. The differences between the thiamine antivitamins in their effect on cell growth in vitro may be due to differences in physicochemical properties and difficulty in DAT transport across the cell membrane.
Subject(s)
Antineoplastic Agents/pharmacology , Enzyme Inhibitors/pharmacology , Pyruvate Dehydrogenase Complex/antagonists & inhibitors , Thiamine/pharmacology , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Apoptosis/drug effects , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , HeLa Cells , Humans , Molecular Structure , Pyruvate Dehydrogenase Complex/metabolism , Structure-Activity Relationship , Thiamine/analogs & derivatives , Thiamine/chemistry , Tumor Cells, CulturedABSTRACT
Malassezia pachydermatis causes infections of the skin and mucous membranes, especially in individuals with metabolic, hormonal, and immunological disorders. The search for M. pachydermatis properties that differentiate isolates from healthy and infected animals may result in the identification of typically commensal and potentially pathogenic strains within the entire species. We aimed to determine and compare protein profiles of M. pachydermatis strains isolated from 30 dogs with clinical symptoms of otitis externa and 34 dogs without symptoms of any disease. Two-dimensional gel electrophoresis was applied, and proteins distinguishing the two groups of strains were identified by liquid chromatography coupled with tandem mass spectrometry. Significant differences were found between potentially pathogenic and commensal isolates. The most significant finding was the presence of nicotinamide adenine dinucleotide phosphate (NADP)-dependent mannitol dehydrogenase and ketol-acid reductoisomerase among M. pachydermatis strains obtained from dogs with otitis externa. Nevertheless, it is not clear whether they are associated directly with the pathogenicity or they play the role of fungal allergen. On the basis of these findings, we can conclude that there may be two distinct groups of M. pachydermatis strains-one typically commensal and the other with properties that enhance the infection process. These results may be used for more precise diagnosis and identification of potentially pathogenic strains in the future.