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American Journal of Clinical Nutrition, Vol 25, 494-498, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.
1 From the Department of Medicine and Department of Clinical Chemistry, Guy's Hospital, London SE1, England and the Alexander Simpson Laboratory for Metabolic Research, St. Mary's Hospital Medical School, London W2, England
A highly sensitive method for the determination of 3-hydroxyanthranilic acid has been used to study the excretion of this metabolite in human urine collected without prior tryptophan loading (spontaneous excretion).
The urinary HA levels were elevated during the development of experimental vitamin B6 deficiency, suggesting that there is an as yet unrecognized pyridoxal phosphate-requiring enzyme beyond the kynureninase step of the tryptophan-nicotinic acid ribonucleotide metabolic pathway. In advanced vitamin B6 depletion, extremely high urinary levels of 3-hydroxykynurenine and kynurenine were accompained by a reduction in spontaneous HA excretion, indicating that at this stage there was a severe impairment of kynureninase activity with reduced synthesis of HA from 3-hydroxykynurenine.
The administration of combined estrogen-progestogen preparations for contraceptive purposes resulted in elevated spontaneous urinary excretions of HA. These abnormal levels were corrected by treatment with pyridoxine.
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