Inhibition of bacterial alpha-glucosidases by castanospermine in pure cultures and activated sludge.
Castanospermine (CAST) is a known and potent inhibitor of various alpha-glucosidases in eukaryotes. In this work, we elucidated whether CAST could also be used for determining bacterial alpha-glucosidase activity, when measured with 4-methylumbelliferyl-alpha- D-glucoside as a substrate, both in a complex bacterial community, in activated sludge and in pure cultures of bacterial isolates. We found that 140 microM CAST inhibited alpha-glucosidase activity by 30% in a pure culture of Pseudomonas stutzeri. The alpha-glucosidase activity in Chryseobacterium gleum was inhibited by 90% at a concentration of 150 microM CAST, whereas the alpha-glucosidase in Paracoccus denitrificans was resistant to the inhibitor. CAST (140 microM) reduced alpha-glucosidase activity in activated sludge by 40%, the respiration rate being reduced by only 12%. No significant inhibition of the respiration rate was observed in Ps. stutzeri or Pa. denitrificans, whereas the respiration rate in C. gleum grown in a medium containing starch was inhibited by 50% with 140 microM CAST. No effect of CAST was observed in C. gleum grown in a complex medium. This indicated that CAST, at the concentration used, did not cause a general negative effect on bacterial activity. The results suggest that the CAST assay may potentially be useful in determining whether alpha-glucosidase activity, starch, poly- and disaccharides contribute appreciably to the overall activity of a bacterial community. However, the assay should not be used for quantitative measurements of such activity.
Mustafa
N
N
Department of Cell and Molecular biology, Microbiology, Göteborg University, P.O. Box 462, 40530 Göteborg, Sweden. Nabaz.Mustafa@gmm.gu.se
Thörn
M
M
Sörensson
F
F
D001419:Bacteria / Q000187:drug effects / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D019069:Cell Respiration; D003470:Culture Media; D007212:Indolizines / Q000494:pharmacology*; D012722:Sewage; D014865:Waste Disposal, Fluid; D014871:Water Microbiology; D000520:alpha-Glucosidases / Q000378:metabolism*; D054836:Indolizidines
D001426:Bacterial Proteins; D003470:Culture Media; D007212:Indolizines; D012722:Sewage; D000520:alpha-Glucosidases; C037806:castanospermine; D054836:Indolizidines