Metarhizium anisopliae produces chitinolytic enzymes which
have been implicated in digestion of the cuticles of the host insect
during the infection process. In this study, enzymatically produced fungal
protoplasts and whole mycelium have been used to study
the cellular location and regulation of these enzymes. Intact mycelium
was
not significantly induced by soluble carboxymethylated
(alkaline) chitin in the production of chitinolytic enzymes. In contrast,
enzymatically produced protoplasts of M. anisopliae were
highly inducible for these enzymes. At 24 h incubation, chitin
induced protoplasts secreted into the medium 76% of total
N-acetylglucosaminidase activity, whereas less than 10% of
chitinase activity was secreted. At 48 h incubation, however,
N-acetylglucosaminidase secretion had dropped to 34% of total
activity, while the proportion of chitinase activity secreted by
protoplasts continued to rise. By 48 h, the majority of chitinolytic enzyme
activity had become cell-bound in both protoplast
preparations and whole cells, and in protoplasts, this activity was mainly
located in the membrane/developing wall fraction. The
influence of the cell wall in the regulation and secretion of these
enzymes is discussed.