COMPUTATIONAL STUDY OF REDUCTION POTENTIAL OF GLUCOSE OXIDASE ENZYME

• Main Author: Kurniawan, Isman
• Format: Theses
• Language: Indonesia
• Subjects: Ilmu alam dan matematika
• Online Access: https://digilib.itb.ac.id/gdl/view/37321
• Institution: Institut Teknologi Bandung

This study focus on investigating the calculation method of reduction potential of oxidoreductase enzyme. The investigated enzyme is Glucose oxidase (GOx) which has FAD (flavin adenine nucleotide) molecule as ligand and redox active site. Reduction potential was calculated using Born-Haber cycle approximation for reduction reaction. The calculation scheme involving free energy and solvation calculation for oxidized and reduced state. Oxidized state was defined as neutral charge molecule and reduced state was defined as radical anion. This study focus on reduction reaction which involving the acceptance of 1 electron by FAD resulting radical anion FAD. Experimental data show that reduction potential of this reaction is -0.200 ± 0.010 V. This data was used as reference to determine the accuracy of calculation. Small model of enzyme was chosen by taking some part of whole enzyme that can represent redox activity of enzyme. This method related to the effort to accelerate calculation time and to investigate the size of calculation model to calculation accuracy. There are 3 models that were used consist of lumichrome molecule, FAD molecule, and FAD molecule with some residue of enzyme that surrounding the active site. Another calculation variable, consist of theory level, basis set, and diffusion function of basis set, was also investigated to explore those contribution to calculation accuracy. The results show that diffusion function of basis set give the biggest contribution to calculation correspond to its reduction potential value. The average of reduction potential value for calculation using diffuse function, which has value -0.749 ± 0.107 V, is closest to the experimental data compare to the other methods. The result related to the existence of anion in the calculaiii tion scheme which its distribution of electron density can be described by diffusion function well. Analysis of calculation model shows that the size of calculation system give the contribution to calculation accuracy. The biggest of the system size, the more accurate of the calculation. That is correspond to the reduction potential value of simplified GOx model, as the biggest model, that has reduction average potential value -1.017 ± 0.265 V. This reduction potential value is closest to the experimental data compare to the other model. This related to electrostatic interaction in non-active site area that cannot be neglected.