Manganese is essential for catalytic activity of Escherichia coli agmatinase

Purified Escherichia coli agmatinase (EC 3.5.3.11) expressed the same activity in the absence or presence of added Mn(2+) (0-5mM). However, it was strongly inhibited by Co(2+), Ni(2+), and Zn(2+) and almost half inactivated by EDTA, Partial inactivation by EDTA yielded enzyme species containing 0.85 +/- 0.1 Mn(2+)/subunit, and it was accompanied by a decrease in intensity of fluorescence emission and a red shift from the emission maximum of 340 nm to 346 nm, indicating the movement of tryptophane residues to a more polar environment. The activity and fluorescence properties of fully activated agmatinase were restored by incubation of dialysed species with Mn(2+). Manganese-free species, obtained by treatment with EDTA and guanidinium chloride (3 M), were active only in the presence of added Mn(2+). Results obtained, which represent the first demonstration of the essentiality of Mn(2+) for agmatinase activity, are discussed in connection with a possible binuclear metal center in the enzyme. (C) 1999 Academic Press.