Lysine 2,3-aminomutase iron-sulfur clusters

Figure 10. EPR spectral evidence for SAM- or SAH-dependent reduction of the iron-sulfur clusters of lysine 2,3-aminomutase. In this figure, AdoMet refers to S-adenosylmethionine (SAM). (A) Spectrum of enzyme in the absence of dithionite and SAM (B) spectrum of enzyme in the presence of dithionite only (C) spectrum of enzyme in the presence of dithionite and SAM (D) spectrum of enzyme in the presence of dithionite and SAH. Adapted from reference 25 with permission from the American Chemical Society.

In contrast to these examples is lysine aminomutase, in which the only significant cluster form observed is the [4Fe-4S] form, although a [3Fe-4S] cluster can be generated upon oxidation. However, no [2Fe-2S] cluster has been reported for this enzyme. LAM is also the only member of this family in which a [4Fe-4S] " cluster has been observed. The iron-sulfur cluster in spore photoproduct lyase has not been characterized, although some evidence for [4Fe-4S] and [3Fe S] forms has been obtained. ... 

Studies on three different iron-sulfur enzyme systems, which all require S-adenosyl methionine—lysine 2,3-aminomutase, pyruvate formate lyase and anaerobic ribonucleotide reductase—have led to the identification of SAM as a major source of free radicals in living cells. As in the dehydratases, these systems have a [4Fe-4S] centre chelated by only three cysteines with one accessible coordination site. The cluster is active only in the reduced... 

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