A protein inhibitor of cellulases in Dictyostelium discoideum

An inhibitor of cellulase (E.C. 3.2.1.4) was isolated from Dictyostelium discoideum in the culmination stage and partially purified. This inhibitor was shown to be a protein of molecular weight 20,000. At pH 6.5 it inhibited the two cellulases present in Dictyostelium but not cellulases from other organisms. Inhibition was prevented at pH 8.0 but could be recovered by adjustment of the pH to 6.5. The inhibitor was present in all stages of development from amoebae to spores but disappeared as the spores aged and was absent from germinating cells indicating that specific destruction of this inhibitor may be responsible for the activation of the cellulases.