人体内共轭叶酸的水解与吸收
The hydrolysis and absorption of conjugated folates in man.
作者信息
Jägerstad M, Dencker H, Westesson A K
出版信息
Scand J Gastroenterol. 1976;11(3):283-7.
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.
摄入生理剂量的合成蝶酰谷氨酸3后，对取自人体门静脉血的血浆中的叶酸形式进行了研究。血浆结合酶通过快速热变性被抑制。用干酪乳杆菌和粪肠球菌对叶酸形式进行测定，并通过薄层色谱法（双向自显影）进行鉴定。在门静脉血浆中证实了单谷氨酸和二谷氨酸叶酸，这表明在结合型叶酸吸收之前肠道会发生水解。对人体胃肠道中的蝶酰多谷氨酸水解酶活性进行了研究。在胃液、胰液和肠黏膜中均证实了该活性。在胰液中发现的活性最高，最适pH为4.5。在胃液中该酶的最适pH为3，活性为胰液中的一半。然而，鉴于每天产生的这些液体的量，生理pH下的活性可能足以水解每日摄入量约为500微克的结合型叶酸。
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