Heterologous expression and biological characteristics of UGPases from Lactobacillus acidophilus

Herein, two genes ( LBA0625 and LBA1719 ) encoding UGPases (UDP-glucose pyrophosphorylase) in Lactobacillus acidophilus ( L. acidophilus ) were successfully transformed into Escherichia coli BL21 (DE3) to construct recombinant overexpressing strains ( E -0625, E -1719) to investigate the biological characteristics of UGPase-0625 and UGPase-1719. The active sites, polysaccharide yield, and anti-freeze-drying stress of L. acidophilus ATCC4356 were also detected. UGPase-0625 and UGPase-1719 belong to the nucleotidyltransferase of stable hydrophilic proteins; contain 300 and 294 amino acids, respectively; and have 20 conserved active sites by prediction. Αlpha-helixes and random coils were the main secondary structures, which constituted the main skeleton of UGPases. The optimal mixture for the high catalytic activity of the two UGPases included 0.5 mM UDP-Glu (uridine diphosphate glucose) and Mg 2+ at 37 °C, pH 10.0. By comparing the UGPase activities of the mutant strains with the original recombinant strains, A10, L130, and L263 were determined as the active sites of UGPase-0625 ( P