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.