Figure 3.
SMP30 catalyzes the interconversion of D-glucono-δ-lactone and D-gluconic acid in the presence of divalent cations including Mn2+, Mg2+, Ca2+, and Zn2+. Opening of the lactone ring releases a proton. Of all the aldonolactone subtrates tested, SMP30 showed the greatest activity with D-glucono-δ-lactone.