Enzyme binding to detect carbohydrate expression in tissue sections. 1. Native and cross-linked glucose oxidase

Enzymes may be useful as highly specific histochemical probes to identify and localize macromolecular substrates in tissue sections. We have used glucose oxidase, a double-headed enzyme, to demonstrate beta-glucosyl groups in paraffin sections. Native glucose oxidase has two active sites per molecule. Soluble polymers formed by glutaraldehyde combine many active binding sites on to one molecule. Some of these bind to glucose in tissue sections, leaving others free to react with chromogenic substrate. The intensity of staining is directly related to the concentration of enzyme, duration of incubation with enzyme, temperature and pH. Polymeric forms of enzyme are about 100 times more effective than native. Glucose oxidase, particularly in a polymeric form, appears a simple reagent for the identification of glucose-containing structures. The use of native and polymerized enzymes as a histochemical probe has enormous potential in the analysis of normal tissues and in the detection of aberrant carbohydrate deposition in pathological tissues; this system serves as a useful model.