The 1-Step NBT/BCIP plus suppressor is a one-component alkaline phosphatase substrate that inhibits endogenous phosphatase activity. This substrate reacts with calf intestinal alkaline phosphatase to produce a dark purple precipitate and is ideal for immunohistochemistry and in situ hybridisation applications.

Two forms of alkaline phosphatase exist in mammals: One form is distributed in a variety of tissues such as the kidney, liver, placenta, bone and tumour; the other form resides in the intestine. These two forms are affected differently by inhibitors. Levamisole added to the substrate inhibits endogenous non-intestinal alkaline phosphatases but does not affect the intestinal form commonly used as a detection label.