Heike Overwin

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An amylosucrase gene was subjected to high-rate segmental random mutagenesis, which was directed toward a segment encoding amino acids that influence the interaction with substrate molecules in subsites -1 to +3. A screen was used to identify enzyme variants with compromised glucan chain elongation. With an average mutation rate of about one mutation per(More)
Glycosylation is one of the most important tailoring reactions for natural products. It typically exerts profound direct or indirect effects on their biological activity. The dihydrochalcone phloretin and its known sugar derivatives, particularly phlori(d)zin, have been shown to influence various cellular processes. We found that a non-Leloir(More)
Two high-level heterologous expression systems for amylosucrase genes have been constructed. One depends on sigma-70 bacterial RNA polymerase, the other on phage T7 RNA polymerase. Translational fusions were formed between slightly truncated versions of the gene from Neisseria polysaccharea and sequences of expression vectors pQE-81L or pET33b(+),(More)
Two biphenyl dioxygenases (BphAs) were shown to catalyze dioxygenation of biphenyldienediol in the nonoxidized ring to form the respective symmetrical biphenyl-bis-dienediol. This novel metabolite served as a growth substrate for both BphA source strains. Its catabolism through the upper bph pathway of Burkholderia xenovorans LB400 was analyzed.
Flavonoids are known to possess a multitude of biological activities. Therefore, diversification of the core structures is of considerable interest. One of nature’s important tailoring reactions in the generation of bioactive compounds is glycosylation, which is able to influence numerous molecular properties. Here, we examined two non-Leloir(More)
Flavonoids are a large group of plant secondary metabolites that exert various biological and pharmacological effects. In this context, the generation of derivatives is of considerable interest. The introduction of hydroxy groups is of particular relevance, as they are known to be involved in many of the biological interactions and furthermore enable(More)
It has repeatedly been shown that aryl-hydroxylating dioxygenases do not possess a very high substrate specificity. To gain more insight into this phenomenon, we examined two powerful biphenyl dioxygenases, the well-known wild-type enzyme from Burkholderia xenovorans LB400 (BphA-LB400) and a hybrid enzyme, based on a dioxygenase from Pseudomonas sp.(More)
The bacterial dioxygenation of mono- or polycyclic aromatic compounds is an intensely studied field. However, only in a few cases has the repeated dioxygenation of a substrate possessing more than a single aromatic ring been described. We previously characterized the aryl-hydroxylating dioxygenase BphA-B4h, an artificial hybrid of the dioxygenases of the(More)