A method for the quanitative determination of dehydropiperidine carboxylic acid, a reduction product of alpha-aminoadipic acid by yeast enzyme

Control of enzyme synthesis in the lysine biosynthetic pathway of Saccharomyces cerevisiae. Evidence for a regulatory role of gene LYS14

Several enzymes of the lysine pathway of Saccharomyces cerevisiae were found to respond to an induction mechanism mediated by the product of gene LYS14 in the presence of 2-aminoadipate semialdehyde, an intermediate of this pathway. This novel regulatory mechanism appears independent of the specific repression by lysine and of the general control of amino acid biosynthesis. Genes LYS1, LYS9 and LYS14 have been cloned and their DNAs used to assay the corresponding messenger RNAs. The results suggest that the induction mechanism, as well as the specific and general regulations, operate at the transcriptional level. The synthesis of saccharopine dehydrogenase (glutamate-forming), previously shown to require the unlinked genes LYS9 and LYS14, is also affected by the induction mechanism. The leaky auxotrophic behaviour of lys14 mutants is explained by the low basal level of expression of LYS9, the structural gene of this enzyme, in the absence of induction by 2-aminoadipate semialdehyde.

Mutation affecting the specific regulatory control of lysine biosynthetic enzymes in Saccharomyces cerevisiae

A Saccharomyces cerevisiae mutant which exhibits a considerably increased cellular lysine pool has been isolated and characterized. Assay of enzymes of the lysine and arginine pathways shows that the mutation harboured by this mutant alters the specific repression of lysine but does not influence the general control of amino acid biosynthesis. Because it is recessive to the wild-type allele and acts pleiotropically on the synthesis of several lysine pathway enzymes, this regulatory mutation has been denominated lys80-1 (or lysR--1). It is believed to affect the synthesis or the structure of a factor which plays a negative role in the control of LYS gene expression.

Lysine biosynthesis in Rhodotorula glutinis: properties of pipecolic acid oxidase

Pipecolic acid oxidase from Rhodotorula glutinis, which converts pipecolic acid to alpha-aminoadipic-delta-semialdehyde, an intermediate of the biosynthetic pathway of lysine, was purified 290-fold. The enzyme from the crude extract and purified preparation exhibited a molecular weight of approximately 43,000 and was composed of a single subunit. The purified enzyme was heat labile and exhibited a pH optimum of 8.5 and an apparent Km for L-pipecolic acid of 1.67 X 10(-3) M. L-Proline acted as a competitive inhibitor for the enzyme. The enzyme was inhibited by the sulfhydryl agents p-chloromercuribenzoate and mercuric chloride. The in vitro enzyme activity required oxygen and upon oxidation of pipecolic acid, oxygen was reduced to hydrogen peroxide.

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.