Methyl hydroperoxide-catalase complex

A property all the primary complexes have in common is the decomposition giving free catalase which does follow first order kinetics (Chance, 71). The velocity constants for ethyl and methyl hydroperoxides are 0.04 and 0.016 sec.-1 as compared with 0.02 sec.-1 for the hydrogen peroxide complex. The secondary complexes decompose far more slowly, the first order velocity constants for ethyl and methyl hydroperoxides having the values 2.3 X 10-4 and 4 X 10-6 sec.-1, respectively. 

Scheme II is preferred because with methyl or butyl hydroperoxides ks > k2 (.101a). Essentially, then, Compound I is not the primary enzyme-substrate complex (161). The formation of Compound I entails the reduction of substrate (peroxide) at the active site (compare Schemes I and II). The recent discovery that nearly one mole of Compound I is formed in the 1 1 reaction between catalase ferriheme and peracetic...

Like peroxidase, catalase forms both primary and secondary complexes with methyl and ethyl hydroperoxide (Chance, 73). The primary complexes are green having a diffuse absorption band in the red starting at 670 mju. The secondary complexes are red and have absorption maxima in the visible region at 572 and 536 mu. The catalase-ethyl hydroperoxide complex found by Stern (74) had maxima at approximately these wavelengths and was thus the secondary complex. The Soret bands of the primary complexes are similar in shape to that of the free enzyme but are shifted toward the red by several millimicrons. At... 

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