A team of international researchers experimented using a non-cryogenic technique to find the structural changes during catalytic reaction of copper amine oxidase.
Enzymes molecules that catalyze the reactions and processes in living organisms are an important source for living beings. To understand its structures and reaction mechanisms is therefore vital to broaden our knowledge and contribute to scientific and medical advances. The researchers Osaka University, Osaka Medical College, Japan Synchrotron Radiation Research Institute (JASRI), and RIKEN have reported the details of structural changes during the catalytic reaction of a copper amine oxidase using a non-cryogenic technique. Their findings were published in the journal Proceedings of the National Academy of Sciences on December 18, 2018.
Previously, the most widely used technique for protein structural determination was X-ray crystallography, where protein crystals are exposed to an X-ray beam leading to diffraction patterns that can be analyzed. However, the cryogenic environment do not allow for thermodynamic analysis of the conformational changes in the protein crystals.
The new study used humid air and glue-coating (HAG) method, where the unfrozen protein crystals were coated with a water-soluble polymer and placed under a stream of humid nitrogen gas with precisely controlled temperature. This helped the crystal to remain stable for analyzing the equilibrium between the structurally distinct conformations of the redox cofactor at any particular temperature.
Toshihide Okajima, corresponding author of the study, said: “As a result of the precise temperature control we were able to achieve, we demonstrated the first successful in crystallo thermodynamic analysis of the working enzyme. Thermodynamic analyses based on crystal measurements give a closer representation of the structural changes than data acquired from solution studies, and are therefore more valuable to our understanding.”