INTESTINAL ALKALINE-PHOSPHATASE CAN TRANSPHOSPHORYLATE THIAMIN TO THIAMIN MONOPHOSPHATE DURING INTESTINAL TRANSPORT IN THE RAT

Intestinal alkaline phosphatase (IAP) purified from calf intestine and IAP present in the brush border membrane of rat small intestine effec tively transphosphorylated thiamin (T) to thiamin monophosphate (TMP) using Na-2-beta-glycerophosphate or Na-2-creatine phosphate as phospha te donors at pH 8.5 TMP production in the brush border membrane was ve ry small and corresponded to 0.001-0.01 percent of the total inorganic phosphate simultaneously released by the enzyme activity. This reacti on, however, could account for TMP formation independently from that m uch more important due to the hydrolysis of thiamin pyrophosphate duri ng T intestinal absorption.