Cyanobacterial carbon metabolism: Fluxome plasticity and oxygen dependence

• DOI: 10.1002/bit.26287
• Publication Date: 2017-03-14T21:23:24Z
• Authors: Ni Wan; Drew M. DeLorenzo; Lian He; Le You; Cheryl M. Immethun; George Wang; Edward E. K. Baidoo; Whitney Hollinshead; Jay D. Keasling; Tae Seok Moon; Yinjie J. Tang
• Keywords: Synechocystis; Metabolic Engineering; Heterologous; Metabolic pathway

Synechocystis sp. strain PCC 6803 has been widely used as a photo-biorefinery chassis. Based on its genome annotation, this species contains complete TCA cycle, an Embden-Meyerhof-Parnas pathway (EMPP), oxidative pentose phosphate (OPPP), and Entner-Doudoroff (EDP). To evaluate how catabolizes glucose under heterotrophic conditions, we performed 13 C metabolic flux analysis, metabolite pool size gene knockouts, heterologous expressions. The results revealed cyclic mode of through the OPPP. Small, but non-zero, fluxes were observed cycle malic shunt. Independent knockouts 6-phosphogluconate dehydrogenase (gnd) enzyme (me) corroborated these results, neither mutant could grow dark conditions. Our data also indicate that metabolism relies upon phosphorylation to generate ATP from NADPH or insufficient light sizes intermediates in particularly acetyl-CoA, found be several fold lower (compared E. coli sizes), while sugar several-fold higher. Moreover, negligible was detected native, heterologous, EDP wild type Δgnd strains Comparing photoautotrophic, photomixotrophic, Calvin OPPP, EMPP possess ability regulate their various growth conditions (plastic), whereas always maintains at low levels (rigid). This work demonstrates genetic profiles do not reflect actual native pathways. Biotechnol. Bioeng. 2017;114: 1593-1602. © 2017 Wiley Periodicals, Inc.