A stuructural gene (ycl) encoding novel yeast cell wall hydrolase, YCL, was cloned from alkalophilic Bacillus alcalophilus subsp. YB380 by PCR, and transformed into E. coli JM83. Based on the N-terminal and internal amino acid sequences of the enzyme, primers were designed for PCr. The positive clone that harbors 1.8 kb of the yeast cell wall hydrolase gene was selected by the colony hybridization method with a PCR fragment as a probe. According to the computer analysis, this gene contained a 400-base-paired N-terminal domain of the enzyme. Based on nucletide homology of the cloned gene, a 850 bp fragment was amplified and the C-terminal domain of the enzyme was sequenced. With a combination of the two sequences, a full nucleotide sequence for YCL was obtained. This gene, ycl, consisted of 1,297 nucleotides with 27 nucleotides with 27 amino acids of signal sequence, 83 redundant amino acids of prosequence, and 265 amino acids of the mature protein. This gene was then cloned into the pJH27 shuttle vector and transformed into the Bacillus subtilis DB104 to express the enzyme. It was confirmed that the expressed cell wall hydrolase that was produced by Bacillus subtilis DB104 was the same as that of the donor strain, by Western blot using polyclonal antibody (IgY) prepared from White Leghorn hen. Purified yeast cell wall hydrolase and expressed recombinant protein showed a single band at the same position in the Western blot analysis.