The hydrolysis and absorption of conjugated folates in man

After ingestion of synthetic PteGlu3 in physiological doses, the folate forms were studied in plasma obtained from human vena portae blood. Plasma conjugase was inhibited by rapid heat-denaturation. The folate forms were assayed with L. casei and S. faecalis and identified by thin-layer chromatography (biautography). Mono- and diglutamic folate was demonstrated in the portal plasma, indicating that intestinal hydrolysis precedes the absorption of conjugated folates. The pteroylpolyglutamate hydrolase activity in the human gastrointestinal tract was investigated. The activity was demonstrated in gastric juice, pancreatic juice, and intestinal mucosa. The highest activity was found in the pancreatic juice with a pH-optimum of 4.5. In gastric juice the pH-optimum for the enzyme was 3 and the activity half of that found in pancreatic juice. However, in view of the volumes of these fluids produced every day, the activity at physiological pH might be enough to hydrolyse the daily intake of conjugated folates in amounts of about 500 mug.