Expression of the alginate lyase gene (aly) from Pseudomonas sp. W7 in Escherichia coli was very high (about 40%) and regulated by catabolite repression. The aly promoter was independent upon activation by cyclic AMP-cAMP receptor protein (cAMP-CRP) complex. When the aly promoter was removed by the construction of pKAL22, alginate lyase, which was under the control of lac promoter in E. coli, was markedly decreased (about 10%). This result confirmed that the aly promoter has stronger expression system in E. coli than lac promoter.