酵母のプロトプラスト化におけるアルカリ性プロテア-ゼの役割

概要

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Alkali-insoluble fraction (AIF), alkali-soluble fraction (ASF), mannan preparation and thermolabile antigenic proteins (TLAa and TLAb) were prepared from the yeast cell wall and incubated with Zymolyase 60000 at various pH ranging from 5.0 to 9.0. AIF was dissolved more rapidly at acidic and neutral pH than at alkali pH (maximum at pH 8.6), but not at pH below 5.4. Mannan preparation was not degradated. TLAa was degradated slightly at pH 5.0 through 9.0. TLAb was not degradated at this pH range. When viable yeast cells were incubated with Zymolyase 60000 in various buffered solutions, the absorbance (A660nm) of the reaction mixture decreased continuously in prolonged incubation at pH 7.0 to 9.0. When the cells were incubated at pH 5.0, no decrease in absorbance occurred beyond 50% of the initial level. This indicates that the cells were still osmotically resistant. When protoplasts were cultured in the presence of Zymolyase, both TLAa and TLAb were released into the medium at pH 6.6_??_6.8, but not at pH 4.8_??_5.0. These findings suggest that the release of cell wall antigenic proteins depends on the susceptibility of ASF to alkali protease in Zymolyase 60000 and that solubilization of ASF is essential for protoplast formation in yeast.
社団法人日本農芸化学会の論文