Silent carrier state

Extensive EPR spectroscopic studies indicate the accessibility of a number of several different enzyme states. Under aerobic conditions, an inactive form is isolated which can show two types of EPR signal, known as Ni-A (unready form) and Ni-B (ready form), as well as containing an EPR-silent form. The ready form can be rapidly activated by H2 in the presence of certain electron carriers, to give the active form... 

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