a) Stimulation of purified sGC by meta-PAL (0.3–100 μM) in the absence and presence of DEA/NO (0.01, 0.1, and 1 μM), YC-1 (30 μM) and ODQ (10 μM) and stimulation of heme-depleted sGC by meta-PAL in the presence of DTT and Mg2+ as cofactor. The specific activity of sGC is expressed as x-fold stimulation vs. basal activity (basal activity in the presence of Mg2+: 152 nmol/mg/min). The data presented represent means ± SEM, from 4 independent experiments performed in duplicate. b) Heme spectra (OD: optic density) of sGC under basal conditions and in the presence of the NO donor DEA/NO and the meta-PAL. These data are representative for three independent determinations.