6.3.2.2 As3+ As3+ coordinately upregulates GCL catalytic subunit and GCL modifier subunit mRNA levels resulting in increased GCL subunit protein expression, holoenzyme formation, and activity. As3+ increases the rate of transcription of both the GCL catalytic subunit and GCL modifier subunit genes and induces the posttranscriptional stabilization of GCL modifier subunit mRNA. The antioxidant N-acetylcysteine abolishes As3+-induced GCL catalytic subunit expression and attenuates induction of GCL modifier subunit. As3+ induction of GCL catalytic subunit and GCL modifier subunit is also differentially regulated by the MAPK signaling pathways and occurrs independent of the Nrf1/2 transcription factors 703807 6.3.2.2 Cu2+ 2 divalent metal ions per enzyme molecule are bound, can be replaced by Mn2+ and Mg2+, binding mechanism and kinetics, overview 652341 6.3.2.2 Cu2+ induces expression of heavy subunit 651393 6.3.2.2 K+ absolute requirement for Mg2+, Mn2+, and K+ ions 706061 6.3.2.2 Mg2+ - 1126, 650713, 651896, 690385, 690440, 690630, 691909, 691912, 692055, 692058, 692442, 692444, 694060, 694485, 694609, 694674 6.3.2.2 Mg2+ 2 divalent metal ions per enzyme molecule are bound, Mg2+ sharpens the substrate specificity, increases the resistance to L-buthionine-S,R-sulfoximine, can be replaced by Mn2+ and Cu2+, binding mechanism and kinetics, overview 652341 6.3.2.2 Mg2+ absolute requirement for Mg2+, Mn2+, and K+ ions 706061 6.3.2.2 Mg2+ absolute requirement, maximal activity at 30-50 mM 1149 6.3.2.2 Mg2+ divalent metal ion required, especially Mg2+, optimal concentration depending on ATP concentration 1120 6.3.2.2 Mg2+ inactive in absence of Mg2+, maximal activity at 10 mM 1126