(A) Comparison of the catalytic activities of β preparations (i) isolated from over-producing Escherichia coli grown in minimal medium supplemented with 50 µM MnCl2 (gray), (ii) depleted of metals by chelation and treated aerobically with 1.5 MnII/β (orange), and (iii) depleted of metals and then treated aerobically with 1.5 MnII/β followed by 1.0 HQ/β (blue). (B) Determination of the MnII equivalence point in activation of metal-depleted β with MnII, O2 (excess), and NQ (1/β). (C) Determination of the NQ equivalence point in activation of the metal-depleted β with 1.5 MnII/β, O2 (excess) and NQ. (D) Suppression of activation in activity assays with the high β concentration (100 µM) by inclusion of 40 µM Vu SOD in the treatments with 1.5 MnII/β O2 (excess), and NQ.