Glucosamine in rhodococci. From metabolism to enzyme precision synthesis

ASENCION DIEZ MD

Congreso; LVI SAIB Meeting - XV SAMIGE Meeting; 2020

Sociedad Argentina de Investigaciones Bioquimicas - Sociedad Argentina de Microbiologia General

The study of pyrophosphorylases (PPase) determining the hexose -1P fate in carbohydrate metabolism is critical for a deeper understanding regarding the use of microorganisms and their enzymes as biotechnological tools. The kinetic and regulatory propertiesof different NDP-hexose PPases from Rhodococcusspp.support this role,and their comparative analysis constitutes an outstanding example.Besides its canonical activity regarded to glycogen synthesis, the rhodococcal ADP-glucose PPase (GlgC) uses glucosamine-1P asanalternative substrate. Curiously, we found that glucosamine-1P activity is allosterically regulated, being glucosamine-6P a main activator. This rhodococcal GlgC response to activation improves its catalytic performance up to metabolic feasibility values.On the other hand, UDP-glucose PPase (GalU) is duplicated in R. jostii(RjoGalU1, RjoGalU2),but R. fascianspresents only one (RfaGalU). All the rhodococcal GalUs are actives as PPases, exhibiting substrate promiscuity toward sugar-1Ps. Remarkably, RjoGalU2 portrays one order of magnitude higher activity with glucosamine-1P than with glucose-1P. The glucosamine-1P activity is also significant in RfaGalU, with similar efficiencies than that observed for glucose-1P. We also analyzed the R. jostii GlmU PPase activity to different sugar-1Ps. Our results support the hypothesis that the partitioning of glucosamine-1P constitutes an uncharacterized metabolic node in Rhodococcusspp. This work supports a scenario for new molecule discovery based on alternatives for carbohydrates metabolism and hypothesizes on evolutionary mechanisms underlying enzyme promiscuity,opening novel metabolic features in (actino)bacteria.