Halsted C H
Am J Clin Nutr. 1979 Apr;32(4):846-55. doi: 10.1093/ajcn/32.4.846.
Dietary folates, existing primarily in the form of pteorylpolyglutamates, are absorbed in the jejunum by a process involving hydrolysis and subsequent intestinal transport of pterolymonoglutamyl folate. Current evidence indicates that one (or more) intestinal mucsoal enzyme(s), termed folate conjugase, is required for the hydrolysis of pteroylpolyglutamate to pteroylmonoglutamyl folate. Unresolved controversies include the mucosal location of hydrolysis (surface versus intracellular), whether the transport of pteroylmonoglutamate is active or passive, and the relation of intestinal mucosal metabolism of pteroylmonoglutamate to its intestinal transport.
膳食叶酸主要以蝶酰多聚谷氨酸的形式存在,在空肠中通过一个涉及蝶酰多聚谷氨酸水解及随后的蝶酰单谷氨酸叶酸肠道转运的过程被吸收。目前的证据表明,一种(或多种)肠道黏膜酶,即叶酸结合酶,是蝶酰多聚谷氨酸水解为蝶酰单谷氨酸叶酸所必需的。尚未解决的争议包括水解的黏膜位置(表面还是细胞内)、蝶酰单谷氨酸的转运是主动还是被动,以及蝶酰单谷氨酸的肠道黏膜代谢与其肠道转运之间的关系。