Mechanism of the nucleoside diphosphate kinase reaction: X-ray structure of the phosphohistidine intermediate

Publisher Summary This chapter focuses on nucleoside diphosphate kinase (NDP kinase) structure and mechanism, the properties of the phosphohistidine form, an obligatory intermediate during catalysis. NDP kinase catalyses the reversible transfer of the terminal phosphate of nucleoside triphosphates to nucleoside diphosphates. NDP kinase is a highly efficient enzyme with little specificity for the base moiety and for the presence of the OH in position 2’ of ribose of the donor and acceptor nucleotides. The activity is high in all cells consistent with a key role for NDP kinase in the biosynthesis of non-adenine nucleoside and deoxynucleoside triphosphate precursors of nucleic acid synthesis, some of that are involved in biosynthetic pathways (UTP, CTP) and in signal transduction (GTP). In NDP kinase, the NTPase activity results from chemical hydrolysis of the reaction intermediate. X-ray structures show that there is no room at the active site for a water molecule to insert between the γ-phosphate of NTP and the histidine. In counterpart, the water attack on the phosphohistidine cannot be prevented by a conformational change of the protein, as in hexokinase.