Role of enzymes in growth and morphology of Neurospora crassa: cell-wall-bound enzymes and their possible role in branching.

The cell wall of Neurospora crassa contains bound enzymes that can digest its structural polymers. These enzymes are not present at the same levels at all stages of growth. The levels of these autolytic enzymes vary and generally show some relationship to the process of branching. These enzymes were removed from the cell wall by beta-mercaptoethanol extraction and were tested for activity against isolated cell wall fractions. Such studies, as well as autolytic studies, showed that enzymes acting on the protein portion of the cell wall (proteases) are more prominent than enzymes that act on the glucan portion (glucanases) of the cell wall. Comparative studies between the wild type and a spreading colonial mutant spco-1 showed that earlier and higher frequency of branching in spco-1 was correlated with a greater amount of these enzymes bound to the cell walls. It is concluded from these observations that autolytic enzymes acting on the protein and glucan portion of the cell walls occur as wall-bound and participate in the process of branching in Neurospora.