Soyasapogenol B is biologically synthesized via two-step hydroxylation of beta-amyrin which is its precursor. However, a gene of the hydroxylase participating in this reaction has not been clarified so far. Therefore, this hydroxylase cannot be utilized in the genetic engineering. It is found out that a sequence corresponding to a soybean-origin cytochrome P450 gene CYP93E1 encodes an enzyme protein which hydroxylates oleanane triterpene at the 24-position. Thus, a method of utilizing this gene by using a genetic engineering means is provided.
