1.14.19.1 Cu2+ - 437646 1.14.19.1 Fe2+ - 437646, 437657, 714029, 714418 1.14.19.1 Fe2+ 20-25% stimulation 437650 1.14.19.1 Fe2+ a di-iron center in cofactor cytochrome b5 745883 1.14.19.1 Fe2+ contains a non-heme iron 437658, 437663 1.14.19.1 Fe2+ contains one atom of non-heme iron per enzyme molecule, catalytic function 437645, 437648, 437657 1.14.19.1 Fe2+ each subunit of homodimer contains one binuclear non-heme iron active site. The reduced DELTA9-desaturase has two approximately equivalent 5-coordinate irons in a distorted square pyramidal geometry, a two-in-two-out equatorial distortion, the irons are rhombic, weakly antiferromagnetically coupled. Addition of substrate causes dramatic changes, first ion remains 5-coordinate but is distorted toward a trigonal bipyramidal structure, second iron changes to 4-coordinate 437670 1.14.19.1 Fe2+ heme and non-heme iron 689882 1.14.19.1 Fe2+ iron-sulfur protein(s) may act as electron carrier(s) in place of the cytchrome b5 and NADH cytochrome b5 reductase system associated with the mammalian desaturase systems 437651 1.14.19.1 Fe2+ required for activity 695472 1.14.19.1 Fe2+ SCD-1 has a di-metal catalytic center consisting of two iron cations (in the crystal structures replaced by zinc cations) that are coordinated by histidine residues and a single water molecule 744416 1.14.19.1 Fe2+ specifically required 437643 1.14.19.1 Mg2+ - 688248 1.14.19.1 additional information enzyme contains active sulfhydryl groups 437658 1.14.19.1 additional information no special ion requirement 437650 1.14.19.1 superoxid dismutase 8% stimulation 437651 1.14.19.1 Zn2+ - 437646 1.14.19.1 Zn2+ 20-25% stimulation 437650 1.14.19.1 Zn2+ incorporation of zinc instead of iron into the protein is likely an artifact of protein overexpression, and zinc remains the predominant metal species even when the growth media and purification solutions are supplemented with iron. Coordination of both zinc ions is consistent with octahedral geometry with one missing ligand. The nine histidines are highly conserved, and eight of them belong to three histidine-containing motifs (two HXXHH motifs and one HX4H motif in SCD1) that are characteristic of integral membrane desaturases 745883