The cellular localization of the constitutive β-glucosidase in the mycelia of Trichoderma viride was investigated by cell fractionation using disrupted mycelia and mycelial protoplasts. In 2-d-old mycelia, approximately 86% of the cellular enzyme activity was detected in the fraction containing cytosol, plasma membrane, and periplasm, and 14% in that containing cell wall. With incubation of the mycelia in a lytic enzyme solution, the β-glucosidase was released rapidly before protoplast formation was observed. After 4 h of incubation in the lytic enzyme solution, only 4% of β-glucosidase activity was detected in the protoplasts recovered. These results indicated that most of the constitutive β-glucosidase was on the cell surface, especially in the cell wall and periplasm.
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