Amino exogenous formation

The rates of formation of various cyclic peptides and DKPs have been documented and shown to be affected by a wide range of physicochemical and structural parameters. Goolcharran and Borchardt examined the effects of exogenous (i.e., pH, temperature, buffer species, and concentration) and endogenous (i.e., primary sequences) factors affecting the rate of cyclic dipeptide formation, using the dipeptide analogues of X-Pro-/)-nitroaniline (X-Pro-/>NA where X represents the amino acid residue of the respective cyclic dipeptide). 

Higher alcohol formation by yeasts has long been attributed to the transamination of exogeneous amino acids to yield the analogous keto acid. For example ... 

Table 1.3. CYCLOSPORIN FORMATION AFTER EXOGENOUS ADDITION OF VARIOUS AMINO ACIDS AS PRECURSORS TO SHAKE CULTURES OF T.

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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