1.14.16.4 Ca2+ activates TPH2 promoter activity 688507 1.14.16.4 Ca2+ the calcium influx through L-type high voltage-activated calcium channels is essential for the full activation of tryptophan hydroxylase leading to melatonin synthesis in the pineal gland 688765 1.14.16.4 Fe2+ - 714213, 716436 1.14.16.4 Fe2+ 0.02 mM, 3.5fold increase in activity 438662 1.14.16.4 Fe2+ 5fold increase in activity 438658, 438661 1.14.16.4 Fe2+ enzyme from pineal gland, stimulation 438654 1.14.16.4 Fe2+ Fe2+ concentration for half-maximal activation of recombinant N-terminal truncated enzyme: 0.0013 mM 438676 1.14.16.4 Fe2+ N- and C-terminal recombinant enzyme, iron is required for activity 438672 1.14.16.4 Fe2+ not required for full activity 438664 1.14.16.4 Fe2+ recombinant pineal enzyme contains 0.2-0.3 mol of iron/mol of enzyme 438675 1.14.16.4 Fe2+ required for activity 671723 1.14.16.4 Fe2+ required for maximal activity 438656 1.14.16.4 Fe2+ some brain enzymes are stimulated others not 438654 1.14.16.4 Fe2+ stimulates in the absence of catalase 438665 1.14.16.4 Fe2+ the iron coordination is a distorted trigonal bipyramidal coordination with His273, His278, and Glu318 (partially bidentate) and one imidazole as ligands. The tryptophan stacks against Pro269 with a distance of 3.9 A between the iron and the tryptophan Czeta3 atom that is hydroxylated 702219