Molecular cloning of the L-phenylalanine transaminase gene from Paracoccus denitrificans in Escherichia coli K-12.

The L-phenylalanine transaminase gene of Paracoccus denitrificans was cloned by a shotgun method using the Escherichia coli K-12 mutant DG30, which lacks three distinct transaminase genes. Plasmid pPAP142 was constructed by inserting a 2.2-kb fragment carrying the transaminase gene into pUC18. Strain E. coli K-12 HB101 cells harboring the plasmid produced 20-fold to 30-fold more transaminase than wild type P. denitrificans cells. The nucleotide sequence of the 2.2-kb fragment was determined, revealing that the deduced amino acid sequence of the transaminase of P. denitrificans is similar to that of other transaminases.