There are many scientific systems used for measuring enzyme activity. The most common enzyme measurement systems are Food Chemical Codex (FCC), United States Pharmacoepia (USP), and Federal Internationale Pharmaceutique (FIP). Each different enzyme measurement system has an enzyme assay method with its own units of measurements. For example, one of the enzyme measurements from protease is HUT (Hemoglobin Unit Tyrosine). Here are some common enzyme activity abbreviations:HUT = hemoglobin unit tyrosine PC = Bacterial Protease Unit DU = apha-amylase dextrinizing unit LU = lipase units PU = phytase units ALU = acid lactase unit CU = cellulase units INVU = inverted unitLacU = lactase activity unit