Diaminopimelic acid lysine biosynthesis from

Nevertheless, an exception to the general rule of retention has recently been discovered in the form of mcfo-a,e-diaminopimelate decarboxylase from Bacillus sphaerkus (259). This PLP-dependent enzyme, which catalyzes the final step in lysine biosynthesis, is the only known amino acid decarboxylase to operate on an a-carbon having the D-configuiation (264). Inversion of configuration was demonstrated for the enzyme from Bacillus sphaerkus by conducting the decarboxylation reaction in H20 solvent and isolating as product (6I7)-l-[6-2H]lysine [Eq. (50)] ... 

There appear to be two pathways for the biosynthesis of lysine among microorganisms. In E. coli there is strong evidence that the diamino dicarboxylic acid, a,e-diaminopimelic acid, is a precursor of lysine. Diaminopimelic acid has been isolated from bacteria - and found to be decarboxylated by a specific decarboxylase occurring in wild-type E. coli. This enzyme has been found to be constitutive rather than adaptive, and it is absent from certain of the lysine auxotrophs. "... 

FIGURE 22-15 Biosynthesis of six essential amino acids from oxalo-acetate and pyruvate in bacteria methionine, threonine, lysine, isoleucine, valine, and leucine. Here, and in other multistep pathways, the enzymes are listed in the key. Note that L,L-a,e-diaminopimelate, the product of step (HI), is symmetric. The carbons derived from pyruvate (and the amino group derived from glutamate) are not traced beyond this point, because subsequent reactions may place them at either end of the lysine molecule. 

Outline of the biosynthesis of the 20 amino acids found in proteins. The de novo biosynthesis of amino acids starts with carbon compounds found in the central metabolic pathways. The central metabolic pathways are drawn in black, and the additional pathways are drawn in red. Some key intermediates are illustrated, and the number of steps in each pathway is indicated alongside the conversion arrow. All common amino acids are emphasized by boxes. Dashed arrows from pyruvate to both diaminopimelate and isoleucine reflect the fact that pyruvate contributes some of the side-chain carbon atoms for each of these amino acids. Note that lysine is unique in that two completely different pathways exist for its biosynthesis. The six amino acid families are screened. 

Alkaloid metabolism in lupine was proved by Wink and Hartmann to be associated with chloroplasts (34). A series of enzymes involved in the biosynthesis of lupine alkaloids were localized in chloroplasts isolated from leaves of Lupinus polyphylls and seedlings of L. albus by differential centrifugation. They proposed a pathway for the biosynthesis of lupanine via conversion of exogenous 17-oxosparteine to lupanine with intact chloroplasts. The biosynthetic pathway of lupinine was also studied by Wink and Hartmann (35). Two enzymes involved in the biosynthesis of alkaloids, namely, lysine decarboxylase and 17-oxosparteine synthetase, were found in the chloroplast stoma. The activities of the two enzymes were as low as one-thousandth that of diaminopimelate decarboxylase, an enzyme involved in the biosynthetic pathway from lysine to diaminopimelate. It was suggested that these differences are not caused by substrate availability (e,g., lysine concentration) as a critical factor in the synthesis of alkaloids. Feedback inhibition would play a major role in the regulation of amino acid biosynthesis but not in the control of alkaloid formation. 

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