Strictosidine Synthase STR

STR family. A 3D structure of this STR was also virtually predicted. An approach called circular permutation was recently applied to get ins ht into the folding, stabiHty, and catalysis of a small library of STRl variants. 

Substrate specificities of strictosidine synthase (STR) analogues from different sources, including heterologous expression, have been invest ted and reported. In summary, from about 30 tryptamine derivatives 10 were converted enzymatically to strictosidine analogues which could give rise to a variety of chemo-enzymatic approaches aiming to the construction of new alkaloids. The built-up alkaloid libraries based on strictosidine synthases was reviewed very recently.  

Besides the STRl complex structures with its natural substrates tryptamine (43), secologanin (44) and the product strictosidine (2), additional X-ray structures of STRl have been resolved. These were complexes of STRl with three unnatural tryptamine analogues. The three ligands were developed as novel substrates of STRl to mimic tryptamine. Especially, to increase the structural diversity of compounds derived from STRl and 

From the overall view of these four STRl complex stmctures with tryptamine (43) and its analogues, it was found that the localization of the three new ligands closely corresponds to that of 43. All of them are arranged around the axis of the propeller, located at the bottom of the STRl activity center. The results points to the fact that aU substrates successfully mimic the natural STRl amine substrate, i.e., to be bound and held in the catalytic center of STRl. 

But for the conformation of all four ligands in a close-up view, several structural reasons and conclusions can be drawn together with observed reactivity issues. They can be explained by a detailed comparison. 

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Fig. 10.1 Reaction catalyzed by strictosidine synthase (Str) in monoterpenoid indole alkaloid formation.

Fig. 6 In vivo reprogramming of alkaloid biosynthesis in hairy roots of C. roseus by introduction of a mutant cDNA of the key enzyme strictosidine synthase (STR) with broader, unnatural substrate specificity leading to diversification of alkaloid content in roots following long-term feeding with 5-substituted tryptamines (X = Cl, Br, Me) [78]...

Figure 7.7 The relative location of c/s-elements and putative transcriptional regulators on the tryptophan decarboxylase (TDC), strictosidine synthase (STR), and cytochrome P450 reductase (CPR) gene promotors from Catharanthus roseus. The black box represents elements responsive to elicitor, jasmonate, or UV light. The white box represents a G-box motif, whereas the striped box represents a GCC-box element.

OUWERKERK, P.B., MEMELINK, J., A G-box element from the Catharanthus rosues strictosidine synthase (Str) gene promoter confers seed-specific expression in transgenic tobacco plants. Mol. Gen. Genet., 1999,261, 635-643. 

The stereospecific condensation of tiyptamine and secologanin under the action of strictosidine synthase (STR), Fig. (4), is the first committed step in TIAs biosynthesis, and it yields the ghicoalkaloid 3-a(S)-strictosidine, which is the central biogenetic precursor of all TIAs [74-11]. 

From Singie to Bunch—From Strictosidine Synthase (STR) to Novel Alkaloids 49... 

Cinchona officinalis Catharanthus roseus Tryptophan decarboxylase (TDC), Strictosidine synthase (STR) Increased quinoline alkaloids in root culture... 

A key reaction in assembly of scaffolds for several classes of alkaloid is the coupling of the amine derived by decarboxylation of an amino acid with a second molecule, the product of which then serves as the precmsor for secondary modifications. Strictosidine synthase (STR) catalyzes the formation of strictosidine, the precursor for monoterpenoid indole alkaloids snch... 

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