3.1.4.12 Ca2+ - 135188, 678083 3.1.4.12 Ca2+ activated by micromolar concentrations of Ca2+ (0.0001 or 0.00001 mM) under Mg2+-free conditions, ceramide generation is dependent upon the calcium ionophore A23187, nSMase is not activated by Ca2+ cations in the presence of 1 mM Mg2+ 705258 3.1.4.12 Ca2+ activation of hemolysis at 2 mM, strong inhibition at 10 mM 651708 3.1.4.12 Ca2+ Km: 0.0191 mM, activation of sphingomyelinase activity in the order of decreasing efficiency Co2+, Mn2+, Mg2+, Ca2+, Sr2+ 665716 3.1.4.12 Ca2+ lysosomal enzyme, stimulation at pH 5-7.5 135163 3.1.4.12 Ca2+ partly restores the EDTA-inhibited enzyme activity 135166 3.1.4.12 Ca2+ plays a role in enzyme regulation by non-substrate lipids 679082 3.1.4.12 Ca2+ slight activation when water-soluble substrates are used 135157 3.1.4.12 Ca2+ slightly activates, Km is 1.40 mM 730073 3.1.4.12 Cd2+ - 135148 3.1.4.12 Co2+ - 135148 3.1.4.12 Co2+ activates 729131 3.1.4.12 Co2+ activates, Km is 1.46 mM 730073 3.1.4.12 Co2+ can replace Mg2+ 650502 3.1.4.12 Co2+ can replace Mg2+, 50% activation at 0.0015 mM 651801 3.1.4.12 Co2+ Km: 0.142 mM, activation of sphingomyelinase activity in the order of decreasing efficiency Co2+, Mn2+, Mg2+, Ca2+, Sr2+. There are three distinct metal ion-binding sites in a long horizontal cleft across the bc-SMase molecule 665716 3.1.4.12 Co2+ lysosomal enzyme, stimulation at pH 5-7.5 135163 3.1.4.12 Co2+ rank-order of increasing activation: Mg2+, Co2+, Mn2+, Zn2+. The four metal ions compete with each other for the same binding site on the enzyme molecule 663762 3.1.4.12 Co2+ required 714926 3.1.4.12 Cu2+ 107% activity at 1 mM Mg2+ 704743 3.1.4.12 Cu2+ 6fold increase in activity at 0.1 mM 652444 3.1.4.12 Fe2+ - 135146 3.1.4.12 Fe2+ 104% activity at 1 mM Mg2+ 704743 3.1.4.12 KCl 1 M, 3fold activation 650323 3.1.4.12 KCl required for full activity 652601 3.1.4.12 Li+ - 135182 3.1.4.12 Mg2+ - 135157, 135170, 135175, 135181, 135184, 135187, 677818, 678083, 678142, 680745 3.1.4.12 Mg2+ 5 mM, activation 651708 3.1.4.12 Mg2+ 5 mM, stimulates 665711 3.1.4.12 Mg2+ 5fold activation of enzyme A and B at pH 7.5 135169 3.1.4.12 Mg2+ absolute requirement for cations such as Mg2+ and Mn2+ 704668 3.1.4.12 Mg2+ absolutely required for activity 650323 3.1.4.12 Mg2+ activates 730060 3.1.4.12 Mg2+ activates the 92000 Da isoform but not the 53000 Da one 135182 3.1.4.12 Mg2+ activates, Km is 1.29 mM 730073 3.1.4.12 Mg2+ activation of plasma membrane and microsomal enzyme 135163 3.1.4.12 Mg2+ approx. 2fold activation of T-mSMase isoforms delta and gamma at 1 mM and 5 mM, respectively, both S-mSMase isoforms epsilon and zeta require 5 mM Mg2+ for maximal activity 652972 3.1.4.12 Mg2+ causes basal activation, reverses EDTA inhibition 135166 3.1.4.12 Mg2+ dependent 135183, 135188 3.1.4.12 Mg2+ dependent on 664877, 693160, 693938, 694260, 716157 3.1.4.12 Mg2+ dependent on, ASMase 680063 3.1.4.12 Mg2+ dependent on, best at 3 mM 679082 3.1.4.12 Mg2+ dependent on, isozyme Sph2 is unique and possesses the Mg2+-binding Glu53 residue in the metal-binding site 730227 3.1.4.12 Mg2+ Km: 0.0161 mM, activation of sphingomyelinase activity in the order of decreasing efficiency Co2+, Mn2+, Mg2+, Ca2+, Sr2+ 665716 3.1.4.12 Mg2+ lysosomal enzyme, stimulation at pH 5-7.5 135163 3.1.4.12 Mg2+ neutral SMase 678434 3.1.4.12 Mg2+ NSMase activity depends on Mg2+ 681268 3.1.4.12 Mg2+ NSMase is dependent on Mg2+ 681266 3.1.4.12 Mg2+ nSMase2 is a Mg2+-dependent neutral sphingomyelinase 678375 3.1.4.12 Mg2+ rank-order of increasing activation: Mg2+, Co2+, Mn2+, Zn2+. The four metal ions compete with each other for the same binding site on the enzyme molecule 663762 3.1.4.12 Mg2+ required 663803, 714410, 714926, 716252, 729171 3.1.4.12 Mg2+ required by N-SMase 716445 3.1.4.12 Mg2+ required by N-SMase for activity 678142 3.1.4.12 Mg2+ required by N-SMase for activity, residues Glu53, Asp126, Asp295, and His296 are critical for Mg2+ binding and catalytic activity 678142 3.1.4.12 Mg2+ required by nSMase1 for activity 678142 3.1.4.12 Mg2+ required for activity 651315, 652601, 653652 3.1.4.12 Mg2+ required for activity, approx. 3fold activation at 0.1-0.5 mM 652090 3.1.4.12 Mg2+ required for activity, Glu53 act as a ligand for the essential Mg2+ 650502 3.1.4.12 Mg2+ required for activity, half-maximal activation at 1 mM 649682 3.1.4.12 Mg2+ required for activity, maximal activation at 2-5 mM 652079 3.1.4.12 Mg2+ required for activity, maximal activation at 5 mM 652373 3.1.4.12 Mg2+ required for activity, maximal activity at 8-16 mM, Km at 3 mM 649984 3.1.4.12 Mg2+ required, 100% activity at 2.5-10 mM Mg2+ 704743 3.1.4.12 Mg2+ required, high concentrations of up to 50 mM of Mn2+ stimulate enzyme activity 750751 3.1.4.12 Mg2+ the enzyme is a Mg2+-dependent neutral sphingomyelinase with two metal ion-binding sites in a long horizontal cleft across the molecule, with one Mg2+ in the central region of the cleft and one divalent metal ion at the side-edge of the cleft. The Mg2+ at the side-edge of the enzyme plays an important role in the binding to membranes 729131 3.1.4.12 Mg2+ two-step activation, high-affinity binding site with 50% saturation at 0.0041 mM, low-affinity-binding site with 50% saturation at 20 mM, approx. 5fold activation at 20 mM 651801 3.1.4.12 Mn2+ - 135148, 135170, 135181, 135183, 135188, 678819 3.1.4.12 Mn2+ 5 mM, activation 651708 3.1.4.12 Mn2+ 5 mM, stimulates 665711 3.1.4.12 Mn2+ absolute requirement for cations such as Mg2+ and Mn2+ 704668 3.1.4.12 Mn2+ activates, most effective divalent metal ion, Km is 0.94 mM 730073 3.1.4.12 Mn2+ activation of plasma membrane and microsomal enzyme 135163 3.1.4.12 Mn2+ can replace Mg2+ 650502 3.1.4.12 Mn2+ can replace Mg2+, 50% activation at 0.00087 mM 651801 3.1.4.12 Mn2+ can replace Mg2+, Km at 2.5 mM 649984 3.1.4.12 Mn2+ can replace Mg2+, maximal activation at 1-2 mM, slight inhibition above 652373 3.1.4.12 Mn2+ can replace Mg2+, maximal activity at 0.5 mM, inhibition above 652079 3.1.4.12 Mn2+ can replace Mn2+ 653652 3.1.4.12 Mn2+ Km: 0.0149 mM, activation of sphingomyelinase activity in the order of decreasing efficiency Co2+, Mn2+, Mg2+, Ca2+, Sr2+ 665716 3.1.4.12 Mn2+ lysosomal enzyme, stimulation at pH 5-7.5 135163 3.1.4.12 Mn2+ nSMase activity of the recombinant protein nSM1 increases 4.5fold in the presence of 0.5 mM Mn2+ 703595 3.1.4.12 Mn2+ rank-order of increasing activation: Mg2+, Co2+, Mn2+, Zn2+. The four metal ions compete with each other for the same binding site on the enzyme molecule 663762 3.1.4.12 Mn2+ required 714926 3.1.4.12 Mn2+ required, 100% activity at 1 mM Mg2+ 704743 3.1.4.12 Mn2+ required, low concentrations of Mn2+ stimulate enzyme activity 750751 3.1.4.12 additional information Ca2+, Co2+, Fe2+, or Zn2+ do not support MA-nSMase activity 704668 3.1.4.12 additional information central metal-binding site residues N77, E119, D265, N267, D374, and H375 are completely conserved in the enzyme 730073 3.1.4.12 additional information Cu2+, Zn2+, and Ni2+ are unable to stimulate activity, nSMase is not activated by Ca2+ cations in the presence of 1 mM Mg2+ 705258 3.1.4.12 additional information metal binding structure, overview 678142 3.1.4.12 additional information Mg2+, Mn2+, Ca2+ and Zn2+, or Ca2+ have no significant effect on the activity 703595 3.1.4.12 additional information not stimulated by Ca2+, CO2+, and Fe3+ 704743 3.1.4.12 additional information the enzyme is dependent on divalent metal ions 729132 3.1.4.12 additional information the order of potency to enhance the activity is Zn2+>Mn2+>Cu2+>Fe2+ 704743 3.1.4.12 Ni2+ - 135148 3.1.4.12 Sr2+ Km: 0.018 mM, activation of sphingomyelinase activity in the order of decreasing efficiency Co2+, Mn2+, Mg2+, Ca2+, Sr2+ 665716 3.1.4.12 Sr2+ slightly activates, Km is 2.42 mM 730073 3.1.4.12 Zn2+ - 135146, 135181, 135186 3.1.4.12 Zn2+ 0.1-0.25 mM stimulates hydrolysis of platelet-activating factor 663974 3.1.4.12 Zn2+ 5fold increase in activity at 0.1 mM 652444 3.1.4.12 Zn2+ activates 730060 3.1.4.12 Zn2+ activates the alk-SMase activity with platelet-inactivating factor, mutation of the metal binding site abolishes the enzyme activity 663974 3.1.4.12 Zn2+ activates the alk-SMase activity with platelet-inactivating factor, mutation of the metal binding site of alk-SMase abolishes the enzyme activity 663974 3.1.4.12 Zn2+ aSMase is processed from a 75-kDa, Zn2+-activated proenzyme to a mature 65 kDa, Zn2+-independent L-SMase 715641 3.1.4.12 Zn2+ binuclear zinc center 751328 3.1.4.12 Zn2+ contains 2 zinc ions 751105 3.1.4.12 Zn2+ contains two zinc ions 750518, 751655 3.1.4.12 Zn2+ contains two Zn2+ ions 751069 3.1.4.12 Zn2+ most of the secreted activity requires Zn2+ for full activity 666964 3.1.4.12 Zn2+ partly restores the EDTA-inhibited enzyme activity 135166 3.1.4.12 Zn2+ rank-order of increasing activation: Mg2+, Co2+, Mn2+, Zn2+. The four metal ions compete with each other for the same binding site on the enzyme molecule 663762 3.1.4.12 Zn2+ required by the secreted enzyme form 716445 3.1.4.12 Zn2+ required for activity, best at 0.5-1 mM, inhibitory above 10 mM 730731 3.1.4.12 Zn2+ slight activation at 4 mM, Km at 2 mM 649984 3.1.4.12 Zn2+ the enzyme possesses at least two different binding sites for Zn2+. Zn2+ binding to the high affinity site can activate the enzyme, whereas the Zn2+ binding to the low-affinity site can activate the enzyme. Binding of the substrate to the enzyme is independent of the Zn2+ binding to the high-affinity site, but is competitively inhibited by the Zn2+ binding to the low-affinity site. Rank-order of increasing activation: Mg2+, Co2+, Mn2+, Zn2+. The four metal ions compete with each other for the same binding site on the enzyme molecule 663762 3.1.4.12 Zn2+ Zn2+ binding to the high-affinity site activates the enzyme and, conversely, binding to the low-affinity site inhibits the enzyme 678142 3.1.4.12 Zn2+ Zn2+-dependent sphingomyelinase acid activity is much higher than Zn2+ independent isoform activity in both fetal and mother's blood 665122