Essentially pure curculin B is disclosed. A process for producing curculin B, includes the steps of: culturing a transformed cell or microorganism containing a recombinant DNA containing a base sequence encoding curculin B, whereby curculin B is produced by the transformed cell or microorganism, and isolating curculin B from the transformed cell or microorganism. A DNA encoding mature or premature curculin B is also disclosed. DNA including a base sequence encoding curculin B, is produced by: separating a fraction containing a curculin B mRNA from Curculigo latifolia, preparing a single-stranded DNA from the mRNA using reverse transcriptase, preparing a double-stranded DNA from the single-stranded DNA, inserting the double-stranded DNA into a vector, transforming a host with the vector to produce a cDNA library, and isolating a cDNA encoding curculin B from the library, using one or more synthesized DNA's containing a base sequence coding for a partial amino acid sequence elucidated from curculin A purified from Curculigo latifolia, as a probe.