文本框: THE STUDY ON USING RAT HEME OXYGENASE-1 MUTANT TO REDUCE THE LEVEL OF BILIRUBIN Xia Z-W, Shao J, Li Y-Z, Chen S-N, Yu S-C Department of Pediatrics, Ruijin Hospital, Shanghai Second Medical University, Shanghai, China Objective: To prepare the rat heme oxygenase-1 (HO-1) mutant and to reduce the level of bilirubin by using this mutated enzyme. Methods: pcDNA3HO1 containing truncated native rat HO-1 cDNA and pcDNA3HO1D25 carrying mutated rat HO-1 cDNA ( His25Ala ) were constructed, respectively. COS-1 cells transfected with pcDNA3HO1 and pcDNA3HO1D25 were collected. The His25Ala mutant and native HO-1 activities were detected and the inhibition of His25Ala mutant was analyzed. Results: Native rat HO-1 was highly expressed in transfected cells and its activity was 13688-15600 units/mg protein per h. However, the enzyme activity of His25Ala mutated HO-1 declined and the value was 1948-2160 units/mg protein per h. While an equal amounts of mutant was added to the enzyme reaction system, the levels of bilirubin decreased 42% of the former. Conclusion: His25Ala mutant reduced the formation of bilirubin and it suggests that the mutant could competely bind the heme with native enzyme. 0893