Background: Ice-binding proteins improve the cold tolerance of cells by inhibiting ice growth and recrystallization. Results: Crystal structure and mutagenesis data of LeIBP suggests the B face as an ice-binding site. Conclusion: LeIBP structure adopts a ␤-helical fold and the aligned Thr/Ser/Ala residues are critical for ice binding. Significance: LeIBP structure can serve as a structural model for a large number of IBPs.

Creatine kinase is a member of the phosphagen kinase family, which catalyzes the reversible phosphoryl transfer reaction that occurs between ATP and creatine to produce ADP and phosphocreatine. Here, three structural aspects of humanbrain-type-creatine-kinase (hBB-CK) were identified by X-ray crystallography: the ligand-free-form at 2.2 Å ; the ADPMg 2+ , nitrate, and creatine complex (transition-state-analogue complex; TSAC); and the ADP-Mg 2+ -complex at 2.0 Å . The structures of ligand-bound hBB-CK revealed two different monomeric states in a single homodimer. One monomer is a closed form, either bound to TSAC or the ADP-Mg 2+ -complex, and the second monomer is an unliganded open form. These structural studies provide a detailed mechanism indicating that the binding of ADP-Mg 2+ alone may trigger conformational changes in hBB-CK that were not observed with muscle-type-CK.

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An enzymatic reaction with supercritical carbon dioxide (SCCO2) as the reaction medium was investigated. Lipase could catalyze the batch type reaction of hydrolysis and interesterification (acidolysis) in SCCO2at 50°C and 29.4 MPa. The time course of interesterification was influenced by the water content as well as by the kind of reaction medium. The initial velocities of hydrolysis and interesterification were greater in SCCO2than in rc-hexane when the water content increased. A part of this difference in reaction velocity was supposed to be due to water, a modifier of the solvent, the solubility of which in SCCO2was estimated to be a hundred times that in rc-hexane.