The Physiological Responses of Triggered by Phosphoribulokinase (PrkA) and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (Rubisco).

Phosphoribulokinase (PrkA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) have been proposed to create a heterologous Rubisco-based engineered pathway in for in situ CO recycling. While the feasibility of a Rubisco-based engineered pathway has been shown, heterologous expressions of PrkA and Rubisco also induced physiological responses in that may compete with CO recycling. In this study, the metabolic shifts caused by PrkA and Rubisco were investigated in recombinant strains where and genes (encodes phosphoenolpyruvate carboxylase and phosphate acetyltransferase, respectively) were deleted from MZLF ( BL21(DE3) Δ, Δ Δ). It has been shown that the demand for ATP created by the expression of PrkA significantly enhanced the glucose consumptions of CC (MZLF Δ) and CA (MZLF Δ, Δ). The accompanying metabolic shift is suggested to be the route (the methylglyoxal pathway) which results in the lactate production for reaching the redox balance. The overexpression of Rubisco not only enhanced glucose consumption but also bacterial growth. Instead of the route, the overproduction of the reducing power was balanced by the ethanol production. It is suggested that Rubisco induces a high demand for acetyl-CoA which is subsequently used by the glyoxylate shunt. Therefore, Rubisco can enhance bacterial growth. This study suggests that responses induced by the expression of PrkA and Rubisco will reach a new energy balance profile inside the cell. The new profile results in a new distribution of the carbon flow and thus carbons cannot be majorly directed to the Rubisco-based engineered pathway.