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T A Fjellstedt

Publications and source records attributed to T A Fjellstedt.

8 recordsLinked to original sources
PubMed1978

Developmental changes in the enzymatic capacity for reduction and oxidation of alpha-ketoadipate in rat liver, heart, kidney, and brain.

alpha-Ketoadipate, an intermediate common to lysine and tryptophan metabolism, is a substrate for both alpha-ketoadipate reductase (alpha-KAR) and alpha-ketoadipate dehydrogenase (alpha-KADH). A comparison was made of the activities of these two enzymes in liver, heart, kidney, and brain of rats during the period from 5 days before birth to 56 days after birth. In general, both enzymes increased in activity during development in all tissues tested; however, different patterns of increase were observed (Figs. 1 and 2). The ratio of alpha-KADH to alpha-KAR (on the basis of activity/g tissue) did not change significantly in liver until day 10 and then increased 6.6-fold (from 0.08 to 0.53) in the period from day 10 to day 28. For other tissues the ratios increased 5.5-fold in hearts (from 0.2 to 1.1), 12-fold in kidney (from 0.2 to 2.4), and 5.3-fold in brain (from 0.3 to 1.6) during the period from day -5 to day 56. These results suggest that alpha-KAR has a major role in the metabolism of lysine and tryptophan during development.

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PubMed1970

Effects of supersuppressor genes on enzymes controlling lysine biosynthesis in Saccharomyces.

Yeast supersuppressor genes capable of masking the effects of several lysine mutant genes (ly(1-1), ly(9-1), ly(2-1)) were studied with respect to their effects on the respective enzymes (saccharopine dehydrogenase, saccharopine reductase, and alpha-amino-adipic acid reductase). In all strains tested, the supersuppressors functioned by allowing enzyme synthesis not found in the unsuppressed mutant. Studies by optical methods of saccharopine dehydrogenase and saccharopine reductase extracted from suppressed ly(1-1) and ly(9-1) cells, respectively, revealed that the K(m) values for these enzymes were significantly greater than those found in wild type. Saccharopine dehydrogenase from suppressed ly(9-1) cells was found to have K(m) values similar to wild type. These findings are consistent with the inference that a supersuppressor may act by enabling nonsense codons to be read, producing altered enzyme protein. Recent findings that lysine degradation in mammals may involve saccharopine and that the human diseases, hyperlysinemia and saccharopinuria, may be due to metabolic blocks in this route of lysine degradation suggest the ly(1-1) and ly(9-1) yeast mutants as models for the human condition and its possible euphenic treatment.

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