[Pig liver transketolase: covalent binding between the coenzyme and protein]

Transketolase from pig liver contains a tightly bound coenzyme, which is not split off after severe treatment (e.g. boiling for 12 hrs in 1 n. HCl, 30 min boiling in 2 n HCl, boiling in 1% DS-Na, standing in 6 M solution of quanidine chloride, etc.). The proteolysis of the enzyme results in a coenzyme-containing material differing in some of its properties from free thiamine by pyrophosphate. The data obtained suggest that pig liver transketolase contains covalently bound thiamine pyrophosphate.