Basic Principles Of Enzyme Histochemistry Lecture Notes - PDF

 ENZYME HISTOCHEMISTRY  Enzyme histochemistry is a morphological techniques that highlights functional alterations  It provides a link between biochemistry and morphology; also furnishes us with information vital to conventional histology, immunohistochemistry and molecular patholo...

 ENZYME HISTOCHEMISTRY  Enzyme histochemistry is a morphological techniques that highlights functional alterations  It provides a link between biochemistry and morphology; also furnishes us with information vital to conventional histology, immunohistochemistry and molecular pathology  Enzyme histochemical techniques involves the biochemical analysis of enzyme activity and information on its topographical localization  General step by step process of enzyme histochemistry includes:  Embedding the tissue in a solution containing substrate of the enzyme to be localized  Followed by the action of the enzyme on the substrate to form a complex  Introduction of a dye or marker compound  The reaction of the dye compound with the complex formed by enzyme-substrate reaction  A colored insoluble product is formed which can be viewed under a light microscope which can further subjected to quantitative analysis Enzyme histochemical Techniques  There are several enzyme histochemical techniques (reactions) which includes: Succinic dehydrogenase, NADH diaphorase, Aminopeptidase, Acid phosphatase, Alkaline phosphatase but will dwell on the most important.  In a dehydrogenase reaction, enzyme substrates like sodium succinate or sodium L - lactate are oxidized and a stoichiometric color indicator tetranitrotetrazolium chloride blue (TNBT) is reduced to black or blue formazan.  The formazan immediately binds to local protein and permits the precise localization of the enzyme dehydrogenase in a particular tissue compartment.  A second group of enzyme reactions use diazonium salt instead of tetrazolium chloride as color indicator  Enzymes stained with this kind of reaction are mainly esterases and phosphatases. The ester group or phosphate group of a naphthyl salt is split off by the enzyme reaction and the naphthyl rest couples to a diazo-salt and stains the esterase- or phosphatase-containing compartment like in a formazan color reaction NOTE:  Almost all enzyme histochemical investigations are performed with frozen tissue, because most enzymes are inactivated by formalin fixation. In fact, formalin fixation is even employed to stop enzyme histochemical reactions like lactic dehydrogenase or succinic dehydrogenase reactions