After enzymatic depolymerization of glycogen by diastase and alpha amylase, what happens to the resulting maltose and glucose during processing?

• A. They are washed out of the section
• B. They remain in the tissue
• C. They convert back to glycogen
• D. They stain with PAS

Answer: (A)

Glycogen detection with PAS relies on the intact glycogen molecule binding Schiff reagent. When diastase and alpha-amylase digest glycogen, it is broken down into maltose and glucose. These small sugar units are water- and alcohol-soluble, so during routine tissue processing (dehydration and clearing), they are washed out of the section. With the substrate removed, there’s no glycogen left to react with the PAS stain, so the section loses the PAS positivity.