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Tryptophan metabolism in vitamin B6-deficient mice

Published online by Cambridge University Press:  09 March 2007

David A. Bender ,
Eliud N. M. Njagi  and
Paul S. Danielian
David A. Bender
Affiliation:
Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WCIE 6BT
Eliud N. M. Njagi
Affiliation:
Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WCIE 6BT
Paul S. Danielian
Affiliation:
Department of Biochemistry, University College and Middlesex School of Medicine, University College London, Gower Street, London WCIE 6BT
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Abstract

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Vitamin B6 deficiency was induced in mice by maintenance for 4 weeks on a vitamin B6-free diet. Tryptophan metabolism was assessed by determining the urinary excretion of tryptophan metabolites, the metabolism of [14C]tryptophan in vivo and the formation of tryptophan and niacin metabolites by isolated hepatocytes. The vitamin B6-deficient animals excreted more xanthurenic acid and 3-hydroxykynurenine, and less of the niacin metabolites N1-methyl nicotinamide and methyl-2-pyridone-4-carboxamide, than did control animals maintained on the same diet supplemented with 5 mg vitamin B6/kg. After intraperitoneal injection of [14C]tryptophan, vitamin B6-deficient mice showed lower liberation of14CO2 from [methylene-14C]tryptophan and [U-14C]tryptophan than did controls, indicating impairment of kynureninase (EC 3.7.1.3) activity. There was no difference between the two groups of animals in the metabolism of [ring-2-14C]tryptophan. Hepatocytes isolated from the vitamin B6-deficient animals formed more 3-hydroxykynurenine and xanthurenic acid than did cells from control animals, but also formed more NADP and free niacin.

Keywords

Tryptophan metabolismVitamin B6 deficiencyMice
Type
Amino acid Metabolism
Information
British Journal of Nutrition , Volume 63 , Issue 1 , January 1990 , pp. 27 - 36
Copyright
Copyright © The Nutrition Society 1990

References

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