A full-length cDNA is obtained by analyzing the partial amino acid sequence of purified endo- beta -galactosidase C, constructing primers based thereon, effecting PCR with the use of the genomic DNA of <i>Clostridium perfringens</i> as a template to thereby obtain a fragment of cDNA encoding endo- beta -galactosidase, effecting cassette PCR by using the cDNA fragment thus obtained to thereby obtain the 5'-terminal and 3'-terminal domains, and further effecting PCR with the use of primers constructed on the basis of the data acquired above.
