Regulatory Properties of the ADP-Glucose Pyrophosphorylase from the Clostridial Firmicutes Member Ruminococcus albus.

ADP-glucose pyrophosphorylase from is encoded by two genes ( and ) leading to a heterotetrameric protein structure, unlike those in other bacterial phyla. The enzymes from two groups of , and , present dissimilar kinetic and regulatory properties. Nevertheless, no ADP-glucose pyrophosphorylase from , the third group in , has been characterized. For this reason, we cloned the C and D genes from 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 enzyme suggested that heterotetrameric ADP-glucose pyrophosphorylases from were unregulated. Our results, together with data from , indicate that heterotetrameric enzymes are mostly regulated. Thus, the ADP-glucose pyrophosphorylase from seems to have distinctive insensitivity to regulation. The enzymes involved in glycogen synthesis from have been less characterized in comparison with other bacterial groups. We performed kinetic and regulatory characterization of the ADP-glucose pyrophosphorylase from Our results showed that this protein that belongs to different groups from (, , and ) presents dissimilar features. This study contributes to the understanding of how this critical enzyme for glycogen biosynthesis is regulated in the group, whereby we propose that these heterotetrameric enzymes, with the exception of , are allosterically regulated. Our results provide a better understanding of the evolutionary relationship of this enzyme family in .