Handbook of Vitamin C Research

In: Handbook of Vitamin C Research ISBN 978-1-60741-874-0Editors: Hubert Kucharski and Julek Zajac© 2009 Nova Science Publishers, Inc.Chapter IIHuman Specific Vitamin C Metabolismand Xenobiotic Polymorphism:The Optimal NutritionYasuo Kagawa + , Shizu Higasa ± , Masaru Tsujimura, Fumio Komatsu,Yoshiko Yanagisawa and Sadahiko IwamotoHigh Technology Center, Kagawa Nutrition University, Sakado, JapanAbstractThe biomedical significance of human vitamin C (VC) metabolism is reviewed inthe light of polymorphisms in xenobiotic enzymes deduced from genetic, biochemical,and epidemiological results to estimate optimal nutrition. VC comprises both ascorbicacid (AsA) and dehydroascorbic acid (DAsA). AsA is oxidized to DAsA via short-livedmonodehydroascorbate radicals in a series of xenobiotic reactions and by reactiveoxygen species (ROS). DAsA is reversibly reduced by glutaredoxin, but is alsoirreversibly hydrolyzed into 2,3-diketo-L-gulonate by dehydroascorbatase [EC 3.1.1.17]and non-enzymatic reactions. VC is a cofactor in reactions catalyzed by Cu + -dependentmonooxygenases [EC 1.13.12.-] and Fe 2+ -dependent dioxygenases [EC 1.13.11.-]. VCplays a protective role against oxidative stress by ROS and xenobiotics, viamonodehydroascorbate radicals. The Vitamin Society of Japan has re-evaluated old databecause of the development of life science. The recommended dietary allowance (RDA)of VC is 100 mg/day for adults in Japan to prevent scurvy. RDA is defined asEAR+2SD, i.e. estimated average requirement (EAR) and the standard deviation (SD)obtained by short-term depletion-repletion studies. However, based on VC synthetic rates+ Manuscript correspondence: Yasuo Kagawa, High Technology Center, Kagawa Nutrition University, 3-9-21Chiyoda, Sakado, Saitama 350-0288, Japan, E-mail: kagawa@eiyo.ac.jp± E-mail of coauthors:higasa@eiyo.ac.jp, tmasaru@eiyo.ac.jp, komatsu@eiyo.ac.jp, yyanagi@jichi.ac.jp,siwamoto@jichi.ac.jp, Fax/Phone: +81-49-282-3618Division of Human Genetics, Jichi Medical School, Shimotsuke, Tochigi 329-0498, Japan