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. 1975 Nov;124(2):893–904. doi: 10.1128/jb.124.2.893-904.1975

Enzymatic lesions in methionine mutants of Aspergillus nidulans: role and regulation of an alternative pathway for cysteine and methionine synthesis.

A Paszewski, J Grabski
PMCID: PMC235981  PMID: 1102536

Abstract

In Aspergillus nidulans the pathway involving cystathionine formation is the main one for homocysteine synthesis. Mutants lacking cystathionine gamma-synthase or beta-cystathionase are auxotrophs suppressible by: (i) mutations in the main pathway of cysteine synthesis (cysA1, cysB1, and cysC1), (ii) mutations causing stimulation of cysteine catabolism (su101), and (iii) mutations in a presumed regulatory gene (suAmeth). A relative shortage of cysteine in the first group of suppressors causes a derepression of homocysteine synthase, the enzyme involved in the alternative pathway of homocysteine synthesis. A similar derepression is observed in the suAmeth strain. Homocysteine synthesized by this pathway serves as precursor for cysteine and methionine synthesis. A mutant with altered homocysteine synthase is a prototroph, indicating that this enzyme is not essential for the fungus.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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