Absorbance changes at 610 nm after flash photolysis of CO from the
two-electron reduced (mixed valence) enzyme in the presence of
O2. The increase in absorbance with a time constant of
≈300 μs is associated with formation of the Pm
intermediate. The same Pm formation rate was obtained with
the SD(I-299) (not shown) as with the SG(I-299) enzyme. Experimental
conditions: 0.1 M Hepes, pH 7.5, 0.1%
dodecyl-β-d-maltoside, ≈2 μM reacting enzyme (the
traces have been scaled to 1 μM reacting enzyme), 1 mM
O2, 22°C.