title: Folding studies of arginine kinase from Euphausia superba using denaturants.
abstract: Arginine kinase (AK) is a key metabolic enzyme for maintaining energy balance in invertebrates and studies on AK from Euphausia superba might provide important insights into the metabolic enzymes in extreme climatic marine environments. A folding study of the AK from E. superba (ESAK) has not yet been reported. To gain insights into the structural and folding mechanisms of ESAK, the denaturants guanidine HCl and urea were applied in this study. We purified ESAK from the muscle of E. superba and evaluated the inhibition kinetics with structural unfolding studies under various conditions. The results revealed that ESAK was almost completely inactivated when using 1.0 M guanidine HCl and 8.25 M urea. The kinetics, characterized via time-interval measurements, showed that the inactivations by guanidine HCl and urea were first-order reactions, with the kinetic processes shifting from monophases to biphases as concentrations increased. Measurements of intrinsic and ANS (anilinonaphthalene-8-sulfonate)-binding fluorescences showed that guanidine HCl and urea induced conspicuous changes in tertiary structures and followed the regular unfolding mechanisms. Our study provides information regarding the folding of this muscle-derived metabolic enzyme and expands our knowledge and understanding of invertebrate metabolisms.
authors.affiliation: College of Biological and Environmental Sciences, Zhejiang Wanli University, Ningbo, 315100, China.
authors.forename: Yue-Xiu
authors.initials: YX
authors.lastname: Si
authors.forename: Nai-Yun
authors.initials: NY
authors.lastname: Fang
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Zhi-Jiang
authors.initials: ZJ
authors.lastname: Wang
authors.forename: Jun-Mo
authors.initials: JM
authors.lastname: Yang
authors.forename: Guo-Ying
authors.initials: GY
authors.lastname: Qian
authors.forename: Shang-Jun
authors.initials: SJ
authors.lastname: Yin
authors.forename: Yong-Doo
authors.initials: YD
authors.lastname: Park
mesh_terms: D000818:Animals; D001122:Arginine Kinase / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D033201:Euphausiacea / Q000201:enzymology*; D019791:Guanidine / Q000494:pharmacology; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D011489:Protein Denaturation / Q000187:drug effects*; D017434:Protein Structure, Tertiary / Q000187:drug effects; D014508:Urea / Q000494:pharmacology
chemical_list: D014508:Urea; D001122:Arginine Kinase; D019791:Guanidine