QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rodden, F. A. Articles by Berg, C. P. Search for Related Content PubMed PubMed Citation Articles by Rodden, F. A. Articles by Berg, C. P.

Enzymatic Conversion of L- and D-Tryptophan to Kynurenine by Rat Liver¹

Department of Biochemistry, College of Medicine, University of Iowa, Iowa City, Iowa 52242

The present communication amplifies our earlier observations that rat liver yields D-kynurenine from D-tryptophan, but much less readily than L-kynurenine from L-tryptophan. The ratios of L- to D-kynurenine production were not altered enough by differential centrifugation or by enzyme purification methods to indicate separation of a "D-tryptophan pyrrolase" from an "L-tryptophan pyrrolase", nor was marked ratio alteration effected by other means. Storage, freezing and thawing, change in pH and heating decreased the kynurenine production from both L- and D-tryptophan; storage with either tryptophan isomer retarded the loss in activity toward both; and intraperitoneal preinjection with either increased the activities toward both. The Michaelis constant found for the conversion of D-tryptophan to D-kynurenine was eight times larger than for the conversion of L-tryptophan to L-kynurenine, the maximum velocity a fourth as large. D-Tryptophan inhibited the production of kynurenine from L-tryptophan, but D-leucine and D-phenylalanine had little or no effect. Lineweaver-Burk plots of overall kynurenine production indicated that the inhibition by D-tryptophan was competitive. The data are interpreted to indicate that the liver pyrrolase system which converts L-tryptophan to L-kynurenine also yields D-kynurenine from D-tryptophan.

KEY WORDS: • liver pyrrolase • D- and L-kynurenine production • competitive inhibition

¹ This report is based on research data obtained by Frank A. Rodden in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biochemistry in the Graduate College of the University of Iowa. We are indebted to the National Institute of Arthritis and Metabolic Diseases for the financial support given us by U. S. Public Health Grants AM 09797 and AM 03141.

² Send requests for reprints to this author.

Manuscript received 9 July 1973.