Di Costanzo Luigi, Pique Michael E, Christianson David W
Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
J Am Chem Soc. 2007 May 23;129(20):6388-9. doi: 10.1021/ja071567j. Epub 2007 May 1.
The crystal structure of the human arginase I-thiosemicarbazide complex reveals an unusual thiocarbonyl μ-sulfide ligand in the binuclear manganese cluster. The C=S moiety of thiosemicarbazide bridges MnA and MnB with coordination distances of 2.6 Å and 2.4 Å, respectively. Otherwise, the binding of thiosemicarbazide to human arginase I does not cause any significant structural changes in the active site. The crystal structure of the unliganded enzyme reveals a hydrogen bonded water molecule that could support proton transfer between a μ-water molecule and H141 to regenerate the nucleophilic μ-hydroxide ion in the final step of catalysis.
人精氨酸酶I-氨基硫脲复合物的晶体结构显示，在双核锰簇中存在一种不寻常的硫代羰基μ-硫化物配体。氨基硫脲的C=S部分分别以2.6 Å和2.4 Å的配位距离桥接锰A和锰B。否则，氨基硫脲与人精氨酸酶I的结合不会在活性位点引起任何显著的结构变化。未结合配体的酶的晶体结构显示出一个氢键水分子，它可以在催化的最后一步支持μ-水分子和H141之间的质子转移，以再生亲核μ-氢氧根离子。
