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 Hunter, J. E. Articles by Harper, A. E. Search for Related Content PubMed PubMed Citation Articles by Hunter, J. E. Articles by Harper, A. E.

Induction of Pyridoxal Phosphate-Dependent Enzymes in Vitamin B-6 Deficient Rats¹

Departments of Biochemistry and Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706

The effectiveness of dietary and hormonal treatments in inducing several pyridoxal phosphate-(PLP)-dependent enzymes has been examined in vitamin B-6 deficient rats. Holo- and apoenzymes of serine dehydratase and ornithine aminotransferase were inducible in both control and deficient rats by feeding them 80% casein diets or by injecting them with glucagon. Holo- and apotyrosine aminotransferase were induced in both control and deficient rats by injecting them with glucagon or with dexamethasone phosphate. Phosphoenolpyruvate carboxykinase, a non-PLP-dependent enzyme, was inducible in both control and deficient rats by glucagon treatment if the rats were fed, but not if they had been starved. The degree of induction of certain enzymes depended upon whether rats were fed ad libitum, starved overnight, or fed a protein-free diet prior to the induction period. Phosphoenolpyruvate carboxykinase activities were about the same in both control and deficient rats. In vitamin B-6 deficient rats, both uninduced and induced activities of serine dehydratase, ornithine aminotransferase, and tyrosine aminotransferase assayed in the presence of PLP, but not in its absence, either equaled or exceeded control values under most experimental conditions. Synthesis of excess of apoenzyme of PLP-dependent enzymes generally accounted for the high total enzyme activity in deficient rats. Differences between values for control and deficient rats could not be accounted for by differences in liver cyclic AMP concentrations nor were they apparently related to reduced food intake of the deficient rats. High apoenzyme concentration during depletion of coenzyme would tend to prevent depletion of active enzyme.

KEY WORDS: • enzyme induction • pyridoxal phosphate • vitamin B-6 deficiency

¹ Research supported by the College of Agricultural and Life Sciences. University of Wisconsin, Madison, and by U.S. Public Health Service grant AM 10748 from the National Institute of Arthritis, Metabolism and Digestive Diseases.

² Present address: The Procter and Gamble Company. Winton Hill Technical Center, 6071 Center Hill Road, Cincinnati, Ohio 45224.

Manuscript received 14 May 1976.