A cDNA for proctase B from Aspergillus niger var. macrosporus was isolated and sequenced. The deduced amino acid sequence (394 residues) of the preproform of the enzyme was highly homologous (98% identify) with those of aspergillopepsins I from A. awamori and A. saitoi, and moderately homologous (68% identity) with that of A. oryzae. Most of the sequence differences were found in the carboxyl-terminal domain.