Structural basis for the Ca2+-enhanced thermostability and activity of PET-degrading cutinase-like enzyme from Saccharomonospora viridis AHK190

• Published in: Applied microbiology and biotechnology Vol. 99; no. 10; pp. 4297 - 4307
• Main Authors: Miyakawa, Takuya, Mizushima, Hiroki, Ohtsuka, Jun, Oda, Masayuki, Kawai, Fusako, Tanokura, Masaru
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2015; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: active sites; Analysis; Binding; Binding sites; Biomedical and Life Sciences; Biotechnologically Relevant Enzymes and Proteins; Biotechnology; calcium; Calcium ions; Conformation; crystal structure; Crystallography; Cutinase; enzymatic hydrolysis; Enzymes; Fungi; Grooves; ions; Life Sciences; Microbial Genetics and Genomics; Microbiology; mutants; Physical properties; Polyesters; Polyethylene terephthalate; polyethylene terephthalates; Proteins; Residues; Saccharomonospora viridis; Studies; Textile fibers; Thermal stability; Thermostability; AHK190; PET hydrolase; activation; Ca; Cutinase-type polyesterase
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-014-6272-8

A cutinase-like enzyme from Saccharomonospora viridis AHK190, Cut190, hydrolyzes the inner block of polyethylene terephthalate (PET); this enzyme is a member of the lipase family, which contains an α/β hydrolase fold and a Ser-His-Asp catalytic triad. The thermostability and activity of Cut190 are enhanced by high concentrations of calcium ions, which is essential for the efficient enzymatic hydrolysis of amorphous PET. Although Ca²⁺-induced thermostabilization and activation of enzymes have been well explored in α-amylases, the mechanism for PET-degrading cutinase-like enzymes remains poorly understood. We focused on the mechanisms by which Ca²⁺enhances these properties, and we determined the crystal structures of a Cut190 S226P mutant (Cut190S²²⁶ᴾ) in the Ca²⁺-bound and free states at 1.75 and 1.45 Å resolution, respectively. Based on the crystallographic data, a Ca²⁺ion was coordinated by four residues within loop regions (the Ca²⁺site) and two water molecules in a tetragonal bipyramidal array. Furthermore, the binding of Ca²⁺to Cut190S²²⁶ᴾinduced large conformational changes in three loops, which were accompanied by the formation of additional interactions. The binding of Ca²⁺not only stabilized a region that is flexible in the Ca²⁺-free state but also modified the substrate-binding groove by stabilizing an open conformation that allows the substrate to bind easily. Thus, our study explains the structural basis of Ca²⁺-enhanced thermostability and activity in PET-degrading cutinase-like enzyme for the first time and found that the inactive state of Cut190S²²⁶ᴾis activated by a conformational change in the active-site sealing residue, F106.