Regeneration of ascorbic acid by rat colon.
Plants and animals alike use ascorbic acid in a variety of reactions that result in net generation of dehydro-L-ascorbic acid. The ability to reduce dehydro-L-ascorbic acid back to ascorbic acid would conserve "total ascorbate" and would help to maintain the toxic oxidized form of the molecule at a low level. This study evaluated the rate of dehydro-L-ascorbic acid reduction either by following the rate of NADPH consumption or by analysis of the amount of 14C-labeled dehydro-L-ascorbic acid converted to ascorbic acid. A large percentage of the NADPH consumed by a semipurified preparation of rat colonic mucosa in vitro was dependent on the presence of dehydro-L-ascorbic acid. The tissue factor active in regenerating ascorbic acid is intermediate in size between cytochrome c and blue dextran. The present results indicate that the mucosa reduced dehydro-L-ascorbic acid by a cytosolic enzyme that uses NADPH as a hydrogen donor. Subsequent to precipitation by ammonium sulfate, the 55-70% fraction contains most of the reductase activity while consisting of only 17% of the cellular soluble protein.
Choi
J L
JL
Intercollege Nutrition Graduate Program, Pennsylvania State University, University Park 16802.
Rose
R C
RC
D000818:Animals; D001205:Ascorbic Acid / Q000096:biosynthesis*; D002474:Cell-Free System; D002850:Chromatography, Gel; D003106:Colon / Q000201:enzymology / Q000378:metabolism*; D005978:Glutathione; D007413:Intestinal Mucosa / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008970:Molecular Weight; D009249:NADP / Q000502:physiology; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D009249:NADP; D010088:Oxidoreductases; C020666:glutathione dehydrogenase (ascorbate); D005978:Glutathione; D001205:Ascorbic Acid