Prion diseases like Creutzfeldt-jakob disease in humans or scrapie in sheep and goats are infectious neurodegenerative diseases. Their infectious agent, called prion, is composed mainly of aggregated and misfolded prion protein and non-proteinaceous components. An example of such a common non-proteinaceous secondary component of natural prions is the polysaccharide scaffold. We studied the influence of such a polysaccharide on the conformational transition of PrP applying an in vitro conversion system. Here we report that glycogen supports and accelerates PrP amorphous aggregation similar to seeded aggregation and leads to co-aggregates. Furthermore, PrP fibril formation was highly accelerated in the presence of glycogen.