INDUCIBLE CHITINOLYTIC SYSTEM OF ASPERGILLUS-FUMIGATUS

Incubation of Aspergillus fumigatus NCPF 2140 in growth medium contain ing 1% chitin as sole carbon source led to induction of specific extra cellular chitinolytic activity of 1.5 mu mol GlcNAc released min(-1) ( mg protein)(-1). The effect was repressed by the inclusion of GlcNAc i n the medium, indicating regulation by a negative feedback mechanism. Extracellular chitinase activity was inhibited by allosamidin (IC50 0. 12 mu M). Multiple chitinolytic enzymes were detected on zymograms of extracellular preparations; levels of individual enzymes induced were dependent upon whether cells were incubated with purified colloidal ch itin or a crude preparation of crystalline chitin. A major, inducible, 45 kDa chitinase was purified using ammonium sulphate precipitation, chitin affinity chromatography and a novel procedure involving the ele ctroelution of the enzyme from a substrate gel containing glycol chiti n. The enzyme is a glycoprotein with endochitinase activity.