Cd- and Zn-NagA were applied to address the incidence of direct interactions of your carbonyl oxygen/sulfur and the metallic ion through a comparison of your kinetic constants for N you can find tyrosine (Y223) and lysine (K139) residues that may additionally be contributing on the conversation with the phosphate moiety https://loginnaga2639381.answerblogs.com/30445517/the-fact-about-naga26-that-no-one-is-suggesting