The isoamylase gene (isoA) from Pseudomonas amyloderamosa was amplified by polymerase chain reaction (PCR), cloned into the pET-3a vector and expressed in Escherichia coli. The enzyme from E. coli was immunologically identical to that from P. amyloderamonas. The use of isopropyl-beta-D-thiogalactoside (IPTG) for indution of the isoA gene expression resulted in an intracellular insoluble aggregate. Active isoamylase preparation was obtained by solubilizing and refolding from the inclusion bodies.