X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) is an inert chromogenic substrate for beta-galactosidase； an enzyme that promotes lactose utilization.；Beta-galactosidase hydrolyzes X-Gal into a colorless galactose and 4-chloro-3-brom-indigo which forms an intense blue precipitate
美
['eksɡ'æl]
