Free tryptophan pool and tryptophan biosynthetic enzymes in Saccharomyces cerevisiae |
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Authors: | Peter A Fantes Lilian M Roberts Ralf Huetter |
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Institution: | (1) Mikrobiologisches Institut der Eidgenössischen Technischen Hochschule, Universitätsstr. 2, CH-8006 Zürich, Switzerland;(2) Present address: Department of Zoology, University of Edinburgh, West Mains Road, EH9 3JN Edinburgh, Scotland |
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Abstract: | The free tryptophan pool and the levels of two enzymes of tryptophan biosynthesis (anthranilate synthase and indoleglycerolphosphate synthase) have been determined in a wild type strain of Saccharomyces cerevisiae and in mutants with altered regulatory properties.The tryptophan pool of wild type cells growing in minimal medium is 0.07 mole per g dry weight. Addition of anthranilate, indole or tryptophan to the medium produces a fifteen- to forty-fold increase in tryptophan pool, but causes no repression of the biosynthetic enzymes. Inclusion of 5-methyltryptophan in the growth medium causes a reduction in growth rate and a derepression of the biosynthetic enzymes, and this is shown here not to be correlated with a decrease in the free tryptophan pool.Mutants with an altered anthranilate synthase showing decreased sensitivity to inhibition by l-tryptophan or by the analogue dl-5-methyltryptophan have a tryptophan pool far higher than the wild type strain, but no repression of indoleglycerolphosphate synthase was observed. Mutants with an anthranilate synthase more sensitive to tryptophan inhibition show a slightly reduced tryptophan pool, but no derepression of indoleglycerolphosphate synthase was found.A mutant with constitutively derepressed levels of the biosynthetic enzymes shows a considerably increased tryptophan pool. Addition of 5-methyltryptophan to the growth medium of non-derepressible mutants causes a decrease in growth rate accompanied by a decrease in the tryptophan pool.Abbreviations CDRP
1-(o-carboxyphenylamino)-1-deoxyribulosephosphate
- paba
paraaminobenzoic acid
- PRA
N-(5-phosphoribosyl)-anthranilate
- tRNA
transfer ribonucleic acid; trp1 to trp5 refer to the structural genes for corresponding tryptophan biosynthetic enzymes |
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Keywords: | Anthranilate synthase Cell permeabilisation Indoleglycerolphosphate synthase Saccharomyces cerevisiae Tryptophan biosynthetic enzymes Tryptophan pool |
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