Constitutive expression of phosphoketolase, a key enzyme for metabolic shift from homo- to heterolactic fermentation in Enterococcus mundtii QU 25

Keisuke Nabeta; Satoru Watanabe; Taku Chibazakura; Takeshi Zendo; Kenji Sonomoto; Mariko Shimizu-Kadota; Hirofumi Yoshikawa

doi:10.12938/bmfh.18-030

Constitutive expression of phosphoketolase, a key enzyme for metabolic shift from homo- to heterolactic fermentation in Enterococcus mundtii QU 25

Biosci Microbiota Food Health. 2019;38(3):111-114. doi: 10.12938/bmfh.18-030. Epub 2019 May 8.

Authors

Keisuke Nabeta¹, Satoru Watanabe¹, Taku Chibazakura¹, Takeshi Zendo², Kenji Sonomoto², Mariko Shimizu-Kadota^{3

1}, Hirofumi Yoshikawa^{1

4}

Affiliations

¹ Department of Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.
² Laboratory of Microbial Technology, Division of Systems Bioengineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
³ Department of Environmental Systems Sciences, Musashino University, 3-3-3 Ariake, Koto-ku, Tokyo 135-8181, Japan.
⁴ NODAI Genome Research Center, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan.

Abstract

Phosphoketolase (PK) is responsible for heterolactic fermentation; however, the PK gene of Enterococcus mundtii QU 25, xfpA, is transcribed constitutively, even under homolactic fermentation conditions. In order to deduce the regulatory mechanisms of PK activity in QU 25, XfpA levels in QU 25 cells under hetero- and homolactic fermentation conditions were tested using western blotting. The results showed that the XfpA protein expression was similar under both conditions and that the expression products formed complexes, most likely homodimers, indicating that the regulation of PK activity is downstream of translation.

Keywords: Enterococcus mundtii; constitutive expression; heterolactic fermentation; homodimer; metabolic shift; phosphoketolase activation; xylose concentration.