INVIVO EXPRESSION OF THE PSEUDOMONAS-STUTZERI MALTOTETRAOSE-FORMING AMYLASE GENE (AMYP)

Northern hybridization and S1 nuclease mapping revealed that the amyP gene coding for maltotetraose-forming amylase of Pseudomonas stutzeri MO-19 is transcribed as a monocistronic mRNA of 2.0 kilobases and that the transcription start site is located 81 base pairs upstream from the first nucleotide of the initiation codon. The amyP gene was expressed weakly in Escherichia coli, and transcription started 49 base pairs downstream of the P. stutzeri MO-19 transcription start site. Synthesis of the amylase in P. stutzeri MO-19 was induced by the addition of maltose to the culture medium and was repressed by the addition of glucose. The induction by maltose was shown to be the result of transcriptional induction of the amyP gene. In contrast, glucose did not repress transcription initiation of amyP, indicating that it controls synthesis of the enzyme, probably at the posttranscriptional level.