Homoserine dehydrogenase threonine sensitive

Starnes, W.L. Munk, P. Maul, S.B. Cunningham, G.N. Cox, D.J. Shive, W. Threonine-sensitive aspartokinase-homoserine dehydrogenase complex, amino acid composition, molecular weight, and subunit composition of the complex. Biochemistry, 11, 677-687 (1972)... 

Veron, M. Falcoz-Kelly E Cohen, G.N. The threonine-sensitive homoserine dehydrogenase and aspartokinase activities of Escherichia coli K12. The two catalytic activities are carried by two independent regions of the polypeptide chain. Eur. J. Biochem., 28, 520-527 (1972)... 

Azevedo, R.A. Smith, R.J. Lea, P.J. Aspartate kinase regulation in maize Evidence for co-purification of threonine-sensitive aspartate kinase and homoserine dehydrogenase. Phytochemistry, 31, 3731-3734 (1992)... 

Paris, S. Wessel, P.M. Dumas, R. Overproduction, purification, and characterization of recombinant bifunctional threonine-sensitive aspartate kinase-homoserine dehydrogenase from Arabidopsis thaliana. Protein Expr. Purif., 24, 105-110 (2002)... 

The pathway of biosynthesis of L-lysine and L-threonine in Corynebacterium glutamicum is shown in Fig. 1. The first step, the formation of phosphoaspartate from aspartate, is catalyzed by aspertokinase and this enzyme is susceptible to the concerted feedback inhibition by L-lysine and L-threonine. The auxotrophic mutant of homoserine (or threonine plus methionine), lacking homoserine dehydrogenase, was constructed and found to produce L-lysine in the culture medium. Second, the mutants which show the threonine or methionine sensitive phenotype caused by the mutation on homoserine dehydrogenase (low activity) was also found to produce appreciable amounts of L-lysine in the culture medium. Furthermore, a lysine analogue (S-aminoethylcysteine) resistant mutant was obtained as an L-lysine producer and in this strain aspartokinase was insensitive to the feedback inhibition. 

Homoserine dehydrogenase activity is required for the synthesis of methionine, threonine, and isoleucine but only threonine serves as a meqor feedback inhibitor. The sensitivity of the enzyme to inhibition by threonine may vary significantly during plant growth, both in different tissues, and among species (Table IV). The progressive reduction of threonine-sensitivity... 

A correlation between the sensitivity of homoserine dehydrogenase to inhibition by threonine and activation by monovalent cations has been demonstrated with preparations derived fi om maize (DiCamelli and Bryan, 1975) and soybeans (Matthews and Widholm, 1979a). The less sensitive the enzyme is to inhibition, the less it will be activated by monovalent ions. Without additional information on the properties of the individual forms of the enzymes, the physical basis of this correlation can not be evaluated. However, monovalent cations appear to have a very different influence on the properties of castor bean homoserine dehydrogenase. With this enzyme, K+ results in minimum activation, but significant inhibition by threonine can be observed in absence of the ion (DiMarco and Grego, 1975). 

Purification of a threonine-sensitive, aspartokinase-homoserine dehydrogenase complex comparisons of the adsorptivities of agarose derivatives as a function of the length of the alkyl chain 60... 

Also functioning as an apparent analog of aspartic semialdehyde, the chloroketone has been reported to specifically inactivate threonine-sensitive homoserine dehydrogenase [C. G. Hirth, M. Veron, C. Villar-Palasi, N. Hurion, and G. N. Cohen, Eur. J. Biochem. 50, 425 (1975)1. 

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