Summary: The gene () encoding pyruvate formate-lyase (Pfl) from was sequenced. The deduced amino acid sequence of Pfl was similar to Pfl, and included the conserved regions necessary for free-radical formation and a catalytic site. The Pfl of appeared to be a free-radical-containing enzyme because of its dioxygen sensitivity and its amino acid sequence similarity with the enzyme. The mRNA of was approximately 2·3 kb and was transcribed in a monocistronic fashion. When cells were grown in batch culture at pH 6·9, the level of transcript increased as the growth phase changed from exponential growth to stationary phase. This result was in constrast to the previous observation that the level of lactate dehydrogenase (Ldh) mRNA decreased during the later stages of growth. Continuous culture experiments conducted at pH 6·9 under glucose-limited and ammonia-limited conditions revealed that mRNA was decreased by an excess supply of glucose, as well as by a high growth rate. On the contrary, mRNA increased when excess glucose was supplied and the growth rate was high. The amount of mRNA in cells was lower at pH 4·5 than pH 6·9, whereas the level of mRNA was higher at pH 4·5. This result was consistent with the amounts of Pfl and Ldh in cells and the proportion of formate and lactate produced. These results support the hypothesis that regulates Pfl and Ldh synthesis at the transcriptional level in response to growth conditions.


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