Regulatory properties of the ADP-glucose pyrophosphorylase from the clostridial Firmicutes Ruminococcus albus

CEREIJO, AE; ASENCION DIEZ, MD; BALLICORA, MA; IGLESIAS, AA

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Año: 2018

0021-9193

ADP-glucose pyrophosphorylase from Firmicutes is encoded by two genes (glgC and glgD) leading to a heterotetrameric protein structure, unlike in other bacterial phyla. The enzymes from two groups of Firmicutes, Bacillales and Lactobacillales, present dissimilar kinetic and regulatory properties. Nevertheless, no ADP-glucose pyrophosphorylase from Clostridiales, the third group in Firmicutes, has been characterized. For this reason, we cloned the glgC and glgD genes from Ruminococcus albus. Different quaternary forms of the enzyme (GlgC, GlgD and GlgC/GlgD) were purified to homogeneity and their kinetic parameters were analyzed. We observed that GlgD is an inactive monomer when expressed alone, but increased the catalytic efficiency of the heterotetramer (GlgC/GlgD) compared to the homotetramer (GlgC). The heterotetramer is regulated by fructose-1,6-bisphosphate, phosphoenolpyruvate, and NAD(P)H. The first characterization of the Bacillales enzyme suggested that heterotetrameric ADP-glucose pyrophosphorylases from Firmicutes were unregulated. Our results, together with data from Lactobacillales, indicate that heterotetrameric Firmicutes enzymes are mostly regulated. Thus, the ADP-glucose pyrophosphorylase from Bacillales seems to have distinctive insensitivity to regulation.