Dephosphorylation of thiamin pyrophosphate by fresh human plasma

Thiamin pyrophosphate was added to human plasma and serum. After various incubations, aliquots were assayed by the thiochrome method. This revealed that fresh human plasma dephosphorylated thiamin pyrophosphate by a reaction that was time and temperature dependent and inhibited by the presence of ethylenediaminetetraacetic acid (EDTA). Fresh plasma did not dephosphorylate pyridoxal-5-phosphate nor the protein bound thiamin pyrophosphate of red cells.