4.6.1.18 Cu2+ crystal structure 134558 4.6.1.18 Cu2+ enhance interaction with substrate but lower stability 134521 4.6.1.18 K+ increases activity 134536 4.6.1.18 K+ optimum activity at 30-50 mM 134482 4.6.1.18 additional information no effect of bivalent cations on enzyme 677904 4.6.1.18 Na+ increases activity 134536 4.6.1.18 Na+ NaCl: 0.1-0.25 M optimum concentration 134538 4.6.1.18 Ni2+ - 134521 4.6.1.18 Ni2+ binds the enzyme, crystal structure 134558 4.6.1.18 sulfate 13 sulfate anions are identified in the electrondensity map of the two dimers in the asymmetric unit of the crystal, confirming that this ion plays a fundamental role in the crystallization process. Four sulfate ions are positioned at the active sites, as typically observed in several other members of the pancreatic-like superfamily, the remaining anions are located on positive patches of the rod surface 728871