Refine
Has Fulltext
- no (5)
Year of publication
- 2003 (5) (remove)
Document Type
- Article (3)
- Doctoral Thesis (2)
Language
- English (5)
Is part of the Bibliography
- yes (5)
Institute
- Institut für Chemie (5) (remove)
The recent work on a variety of family 18 chitonolytic enzymes has yielded important data concerning the structure, substrate-binding, catalysis, inhibitor-binding and even dynamics. These data have been useful in helping to better understand the roles of various types of chitinases in chitin hydrolysis, to rationally engineer the properties of these enzymes, thus making them more suitable as biocatalysts, and to study and understand the effectiveness of natural and designed chitinase inhibitors, which may be of medical interest. On the other hand, the recent work on ChiB shows that catalysis in family 18 chitinases is a highly complicated process, involving larger parts of the enzyme and dynamics. Thus, despite recent discoveries, there is still a lot more to discover about how these enzyme work.
The soln.-state conformations of N,N',N''-triacetyl chitotriose (1) and other potential chitinase inhibitors 2-4 were studied using a combination of NMR spectroscopy (NOESY) and mol. mechanics calcns. Detn. solely of the global energy min. conformation was found to be insufficient for an agreement with the NMR results. An appropriate consistency between the NMR exptl. data and theor. calcns. was only reached by assessing the structures as population-weighted av. conformers based on Boltzmann distributions derived from the calcd. relative energies. Analogies, but also particular differences, between the synthetic compds. 2-4 and the naturally-occurring N,N',N''-triacetyl chitotriose were found. Furthermore, the conformation of compds. 1 and 2 when bound to hevamine was also studied using transferred NOESY expts. and the binding process was found to impart a level of conformational restriction on the ligands. The preferred conformation as detd. for 1 in the bound state to hevamine belonged to one of the conformational families found for the compd. when free in soln., although full characterization of the bound-state conformations was impeded due to severe signal overlap. Satn. transfer difference NMR expts. were also employed to analyze the binding epitopes of the bound compds. We thus detd. that it is mainly the acetyl amido groups of the trisaccharide and the heterocyclic moiety which are in close contact with hevamine.
From the stem bark of Erythrina burttii, a new isoflavone, 5,2',4'-trihydroxy-7-methoxy-6-(3- methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4'-methoxy- 3'-(3-methylbutadienyl)-5'-(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were detd. on the basis of spectroscopic evidence.