THE PURIFICATION AND PROPERTIES OF A COPPER NITRITE REDUCTASE FROM HALOFERAX DENITRIFICANS

A dissimilatory nitrite reductase from Haloferax denitrificans was pur ified to apparent electrophoretic homogeneity, The overall purificatio n was 125-fold with about a 1% recovery of activity, The enzyme, which had a molecular mass of 127 kDa, was composed of a 64-kDa subunit as determined by SDS-PAGE, Although maximum activity occurred in the pres ence of 4 M NaCl, no activity was lost when the enzyme was incubated i n the absence of NaCl, The absorption spectrum had maxima at 462, 594, and 682 nm, which disappeared upon reduction with dithionite. Diethyl dithiocarbamate (DDC) was inhibitory, and the addition of copper sulfa te to DDC-inhibited enzyme partially restored activity, These results suggest this enzyme is a copper-containing nitrite reductase and is th e first such nitrite reductase to be described in an Archeon.