Reductive dechlorination of trichloroethylene by the CO-reduced CO dehydrogenase enzyme complex from Methanosarcina thermophila

Trichloroethylene (TCE) was reductively dechlorinated to cis-dichloroethylene, trans-dichloroethylene, 1,1-dichloroethylene, vinyl chloride, and ethylene by the CO-reduced CO dehydrogenase enzyme complex from Methanosarcina thermophila; the apparent K_m and V_max values were 1.7 ± 0.3 mM TCE and 26.2 ± 1.7 mol TCE dechlorinated/min/mmol factor III. Factor III also catalysed the dechlorination of TCE when in the presence of titanium(III) citrate; the apparent K_m and V_max values were 1.2 ± 0.3 mM TCE and 34.9 ± 3.6 mol TCE dechlorinated/min/mmol factor III. The enzyme complex was resolved into the two-subunit nickel/iron-sulfur (Ni/Fe-S) component and the two-subunit factor III-containing corrinoid/iron-sulfur (Co/Fe-S) component. The Ni/Fe-S component was unable to dechlorinate TCE in the presence of CO; however, reconstitution with the Co/Fe-S component yielded the same dichlorinated products as with the CO dehydrogenase enzyme complex.