On catalase activity in spores of Aspergillus niger

Summary

• 1. A study has been made of the catalase activity of the spores of Aspergillus niger, NRRL 599. The enzyme occurs in 2 forms in the spores: (a) readily accessible, as evidenced by the activity of untreated whole spores and (b) difficultly accessible, as represented by that component which becomes fully reactive when the spores are disrupted or reactive to varying degrees on treatment with dioxane or one of the surface active agents, deoxycholate, digitonin and triton X-100. The latter form constitutes over twice the former. Barring dioxane treatment, conventional techniques failed to solubilize the enzyme.

• 2. The two forms of catalase differ in some properties, the most important of which is the behaviour on heating for 5 min at 70°C. The accessible form undergoes inactivation to a considerable extent, whereas the inaccessible form is not significantly affected. The heat sensitive part of catalase tends to be associated with particles sedimenting from aqueous homogenates at the lowest relative centrifugal forces. The accessible form is also preferentially sensitive to storage at room temperature or in a Deep-freeze. A part of the accessible form is soluble in dioxane; the rest is insoluble. However, no distinction between the two forms was demonstrable on the basis of pH-activity relationship or inhibition by cyanide and fluoride.

• 3. These properties could be largely accounted for by assuming that the greater part of catalase of spores is firmly bound to structural elements in the spores such as the spore coat and that the rest is east is easily accessible by occurring at the openings on this structure.