Nonenzymatic glycosylation (glycation) of proteins is a multistage chemical process starting as a condensation reaction between reducing sugars and primary amino groups (mainly from the side chains of Lis and Arg) and ending up with formation of complex heterocyclic compounds called advanced glycation end products (AGEs). For a long time, glycation has been attributed to the long-lived eukaryotes (including in humans) only. In a recent study, we showed that glycation also occurs in bacteria. The present study aims to prove that bacterial cytoplasm contains soluble glycating compounds. To this end, Lis/Arg-rich histone H1 isolated from rat liver was treated with deproteinized Escherichia coli cytoplasm through a dialysis membrane. This treatment leads to accumulation of AGES as well as to a remarkable degradation of the reporter protein on storage at 4degreesC. Our results indicate also that glycation can be inhibited by acetylsalicylic acid (aspirin), thiamine (vitamin B1), and pyridoxine (vitamin B6).