The present invention provides a process for producing isoprenoid compounds or proteins encoded by DNA using DNA that contains one or more of the DNA encoding proteins having activity to improve efficiency in the biosynthesis of isoprenoid compounds effective in pharmaceuticals for cardiac diseases, osteoporosis, homeostasis, prevention of cancer, and immunopotentiation, health food and anti-fouling paint products against barnacles; the DNA; the protein; and a method for screening a substance with antibiotic and weeding activities comprising screening a substance inhibiting enzymatic reaction on the non-mevalonate pathway.