An aspartic proteinase from Fusarium moniliforme. Purification and general properties

An acid proteinase from the culture filtrate of Fusarium moniliforme was purified by acetone precipitation, gel filtration and ion-exchange chromatography. The final enzyme preparation was homogeneous on polyacrylamide gel electrophoresis. The apparent molecular weight was estimated to be 38 000, based on sodium dodecyl sulfate gel electrophoresis and an isoelectric point of pH 4.90. The optimum pH was found to be 3.2 when measured with denatured hemoglobin as substrate. The enzyme showed maximum stability in the pH range 3.0-5.5. Pepstatin, 1,2-epoxy-3-(p-nitrophenoxy)propane and diazoacetyl-DL-norleucine methyl ester strongly inhibited the proteinase activity, whereas thiol reagents, serine-type proteinase inhibitors and metal-chelating reagent had no significant effect. The data indicate that the proteinase from F. moniliforme is an aspartic proteinase which possesses milk-clotting activity.