Expression of catalytic subunit of bovine enterokinase in the filamentous fungus Aspergillus niger

The cDNA encoding for catalytic subunit of bovine enterokinase (EKL), to wh ich the sequence for Kex2 protease cleavage site was inserted, was expresse d in the protease deficient filamentous fungus Aspergillus niger AB1.13. Fu ngal transformants were obtained in which expression of the glucoamylase fu sion gene resulted in secretion of the protein into growth medium. Fusion p olypeptide was processed to mature EKL by endogenous Kex-2 like protease cl eavage during secretory pathway. The highest quantity of EKL, up to 5 mg l( -1), was obtained in soya milk medium. The secreted EKL was easily purified from other proteins found in A. niger culture supernatant, using ion excha nge and affinity chromatography. The yield of the purified and highly activ e EKL was 1.9 mg l(-1) of culture. (C) 2000 Elsevier Science B.V. All right s reserved.