Activated Peroxidase is horseradish peroxidase (HRP) enzyme, whose native carbohydrates (sugars) have been gently oxidized with periodate to produce amine-reactive aldehyde groups. These carbonyls of Activated Peroxidase spontaneously and efficiently crosslink with primary amines on antibody or other proteins. The method is more effective than other amine-reactive chemistries, such as glutaraldehyde coupling, which often causes polymerization and a greater degree of conjugate inactivation. The pre-activated enzyme eliminates the difficulties inherent in preparing and validating activated peroxidase from scratch.