B3GALT5 and cancer: To improvethe efficiency, we explored the two human galactosyltransferase (β3GalT5)isozymes in cancer cells for this reaction and found that isozyme1 (β3GalT5–1) is more active than isozyme 2 (β3GalT5–2).We then identified a common soluble domain of the two β3GalT5isozymes as a candidate and evaluated the activity and substrate specificityof the glycosylated and nonglycosylated glycoforms.