Abstract: To investigate the possibility of high-level production of UQ,ubiCA genes, which encodes enzymes for the first two steps of UQ biosynthesis in Escherichia coli were overexpressed.Five expression plasmids containing ubiCA were constructed and transformed into E.coli JM83 or BL21(DE3).Different expression of ubiCA genes resulted in an increase in UQ production to various degrees.Among them the expression under ubiC promoter(pubiCA-lacZF) was most effective. Accordingly we succeeded in achieving a level of UQ production(3.5) times that of the control.Meanwhile,the result suggests that the high-level expression of ubiCA gene is probably related to the sequence of its own promoter.