Methionine overproduction

Towards methionine overproduction in Corynebacterium glutamicum - methanethiol and dimethyld-isulfide as reduced sulfur sources. 

Morzycka E, Sawnor-Korszynska D, Paszewski A, Grabski J, Raczynska-Bojanowska K. Methionine overproduction by Saccharomyces lipolytica. Appl Environ Microbiol 1976 32 125-30. 

The enzymes and control sites in the conversion of aspartate to 0-phosphohomoserine, and in the further metabolism of this branch-point intermediate to threonine and isoleucine have been covered in detail in the previous chapter. Here, those aspects of special relevance to methionine biosynthesis will be discussed. A proposed scheme for the control of methionine biosynthesis is presented in Fig. 6. In this scheme, the primary signal that overproduction of methionine has occurred in an increased concentration of AdoMet, which allosterically stimulates threonine synthase and thereby diverts 0-phosphohomoserine into the synthesis of threonine rather... 

Many plant proteins are of limited nutritional value because of their low content of methionine, which is one of the first essential amino acids to become inadequate in the human diet (Allaway and Thompson, 1966). In spite of the uncertainties of the regulatory scheme shown in Fig. 6, it should provide a useful working model for a rational approach to increasing the methionine content of plants. For example, if the scheme is correct, an overproduction of methionine should result from inhibition of the conversion of methionine to AdoMet, and/or from reducing the allosteric stimulation of... 

Methionine biosynthesis is controlled by the metabolic regulation of enzymes in the pathway. Species of Corynebacterium and Brevibacterium have much simpler regulatory mechanisms than E. coli for methionine biosynthesis and are the preferred microbes for overproduction. Aspartokinase is a major enzyme that catalyzes the phosphorylation of aspartic acid and redirects the flux to aspartate family of amino acids. 

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