Enzyme Histochemistry

Enzyme Histochemistry

• Enzyme histochemistry is a morphological technique that highlights functional alterations in tissues.
• It provides a link between biochemistry and morphology, and furnishes vital information for conventional histology, immunohistochemistry, and molecular pathology.

Steps in Enzyme Histochemistry

• Embedding the tissue in a solution containing the substrate of the enzyme to be localized.
• The enzyme acts on the substrate to form a complex.
• Introduction of a dye or marker compound.
• The reaction of the dye compound with the enzyme-substrate complex forms a colored insoluble product.
• The product can be viewed under a light microscope and subjected to quantitative analysis.

Enzyme Histochemical Techniques

• There are several enzyme histochemical techniques, including Succinic dehydrogenase, NADH diaphorase, Aminopeptidase, Acid phosphatase, and Alkaline phosphatase.
• Dehydrogenase reactions use enzyme substrates like sodium succinate or sodium L-lactate, which are oxidized, and a stoichiometric color indicator tetranitrotetrazolium chloride blue (TNBT) is reduced to black or blue formazan.
• The formazan binds to local protein, allowing precise localization of the enzyme dehydrogenase in a particular tissue compartment.
• Diazonium salt is used as a color indicator in a second group of enzyme reactions, primarily for esterases and phosphatases.