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THE ABSORPTION OF BOUND FORMS OF B‐GROUP VITAMINS BY RAT INTESTINE
Author(s) -
Turner J. B.,
Hughes D. E.
Publication year - 1962
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1962.sp001583
Subject(s) - thiamine pyrophosphate , thiamine , cofactor , flavin group , riboflavin , flavin mononucleotide , biochemistry , pyrophosphate , biocytin , chemistry , nucleotide , enzyme , nicotinamide mononucleotide , biology , nad+ kinase , nicotinamide adenine dinucleotide , neuroscience , gene , central nervous system
The rates of movement of bound forms of B‐group vitamins (coenzyme A, thiamine pyrophosphate, diphosphopyridine nucleotide, flavin mononucleotide and biocytin) from the mucosal to serosal fluids has been measured in everted sacs of rat jejunum. Thiamine pyrophosphate, biocytin and flavin mononucleotide move at approximately the same rates as the free vitamin: there was no indication of active transport. The results thus resemble those obtained with free vitamins alone and suggest that these bound forms are absorbed by passive diffusion. Diphosphopyridine nucleotide, coenzyme A and, to a lesser extent, flavin mononucleotide were rapidly degraded to free forms of the vitamins. The breakdown of the pyridine nucleotide was studied in cell‐free extracts of intestinal mucosa and has been shown to be due mainly to a DPN'ase type of enzyme, although a nucleotide pyrophosphorylase is also present. Some breakdown of biocytin to form free biotin was also found. Negligible breakdown of thiamine pyrophosphate was detectable under these conditions.