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Effect of tryptophan metabolites on the activities of rat liver pyridoxal kinase and pyridoxamine 5-phosphate oxidase in vitro.

Authors: Takeuchi, F  Tsubouchi, R  Shibata, Y 
Citation: Takeuchi F, etal., Biochem J. 1985 Apr 15;227(2):537-44.
Pubmed: (View Article at PubMed) PMID:2988502

Pyridoxal kinase was purified 4760-fold from rat liver. The Km values for pyridoxine and pyridoxal were 120 and 190 microM respectively, and pyridoxine showed substrate inhibition at above 200 microM. Pyridoxamine 5-phosphate oxidase was also purified 2030-fold from rat liver, and its Km values for pyridoxine 5-phosphate and pyridoxamine 5-phosphate were 0.92 and 1.0 microM respectively. Pyridoxine 5-phosphate gave a maximum velocity that was 5.6-fold greater than with pyridoxamine 5-phosphate and showed strong substrate inhibition at above 6 microM. Among the tryptophan metabolites, picolinate, xanthurenate, quinolinate, tryptamine and 5-hydroxytryptamine inhibited pyridoxal kinase. However, pyridoxamine 5-phosphate oxidase could not be inhibited by tryptophan metabolites, and on the contrary it was activated by 3-hydroxykynurenine and 3-hydroxyanthranilate. Regarding the metabolism of vitamin B-6 in the liver, the effects of tryptophan metabolites that were accumulated in vitamin B-6-deficient rats after tryptophan injection were discussed.

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CRRD Object Information
CRRD ID: 2303018
Created: 2009-01-27
Species: All species
Last Modified: 2009-01-27
Status: ACTIVE



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