Comparing the Efficiency of 3-ketosteroid delta(1)-dehydrogenase and Cholesterol Oxidase at Degrading 7-Ketocholesterol

Medical bioremediation is a process that uses microbial enzymes to supplement the body’s natural catabolic processes in order to dispose of damaging substances. This study compares the efficiencies of two microbial enzymes: Cholesterol Oxidase (CO) from Chromobacterium sp. DS-1 and 3-ketosteroid delta(1)-dehydrogenase (KstD) from Rhodococcus erythropolis, at degrading one such harmful substance, 7-ketocholesterol (7KC). Based on existing literature, we hypothesized that hydrophobic interactions between the active sites of these enzymes and 7KC likely dictate enzyme efficiency. Two metrics of enzyme efficiency were analyzed: binding affinity for the ligand and Gibbs free energy of the enzymatic reaction. KstD was found to have a greater binding affinity with a pKd value of 7.88 (std. ± 0.63) compared to 6.55 (std. ± 0.35) for CO and a lower ΔG of -10.64 kcal/mol (std. ± 0.85) compared to -8.84 kcal/mol (std. ± 0.47) for CO. These values suggest that KstD is more efficient at degrading 7KC than CO. Results from this study may be used to design a more effective treatment for age-related diseases associated with the build-up of 7KC.