Induction of Rhizopus oryzae pyruvate decarboxylase genes.

Two pyruvate decarboxylase genes, pdcA, and pdcB, were cloned from Rhizopus oryzae. These genes are similar to each other with approximately 85% nucleotide sequence identity within the coding region. Multiple transcriptional start sites and polyadenylation sites were found for both genes. The deduced translation product of each gene results in a 561 amino acid protein with approximate molecular weight of 61 kDa each. The amino acid identity between the two proteins was 91% as calculated by Lipmann-Pearson comparisons. Transcriptional control appears to be important in regulation of the PDC, since much of the transcript accumulation parallels enzymatic activity. There was no detectable pdc transcript from cultures grown in glycerol-containing medium. Induction of transcription for pdcA and pdcB was initiated within 1.5 h of adding glucose to the culture. Shifting the aerobically grown cultures to anoxic conditions at this time resulted in enhanced pdc transcription, PDC enzymatic activity, and ethanol production, compared to cultures with continued aerobic growth.