Effect of the microtubule inhibitor methyl benzimidazol-2-yl carbamate (MBC) on production and secretion of enzymes in Aspergillus nidulans

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The effect of the antimicrotubular drug methyl benzimidazol-2-yl carbamate (MBC) on the production and secretion of acid phosphatase, α-galactosidase and β-galactosidase in Aspergillus nidulans was studied. A wild type and two benomyl resistant mutant ( benA10 and benC28 ) strains were used. All the strains secreted acid phosphatase and α-galactosidase into the culture medium, whereas β-galactosidase remained in the mycelium with a portion of its activity bound to the cell wall. When the wild type strain was incubated in the presence of a sublethal dose of MBC, a decrease of the activity of the enzymes studied was found. A reduction in the secretion of acid phosphatase and α-galactosidase into the culture medium was also observed. In addition, a decrease in the percentage of α- and β-galactosidase activities bound to the cell wall was detected. The MBC dose used for the wild type strain did not modify either the total enzyme activities or the secretion of the enzymes studied in the benomyl resistant mutant benA and benC strains. However, when those strains were grown in the presence of a sublethal dose of MBC, a decrease in the total enzyme activities as well as a reduction in acid phosphatase and α-galactosidase secretion was found. In addition, alterations in the percentage of enzyme activities bound to the cell wall were observed in both mutant strains. Results described in this work, clearly suggest that microtubules are involved in the polarized secretion of enzymes in A. nidulans .