Investigations on cellular nanoparticles required for synthesis of chitin the precursor for chitosan

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Title: Investigations on cellular nanoparticles required for synthesis of chitin the precursor for chitosan
Authors: Kajla, Mayur Kumar
Thesis advisor: Prof. Dr. Hildgund Schrempf
Thesis referee: Prof. Dr. Jürgen Hofemeister
Abstract: In the presented studies, chitin synthase containing nanoparticles (chitosomes) from the yeast Saccharomyces cerevisiae lacking the chs3 gene were investigated. Two step centrifugations using sucrose gradients led to considerable purity of the chitosomal complexes. Chitin synthase I activity was determined via a previously described ELISA based WGA assay and a novel assay using the Streptomyces chitin binding protein CHB1, which provided good tools to follow the purification procedure. In collaboration, it could be shown that the complexes produce fibers in the presence of the substrates uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc) and N-acetylglucosamine (GlcNAc) and this reaction was inhibited by addition of chitin synthase inhibitor nikkomycin Z. These results demonstrate for the first time that CSI containing chitosomes can be gained. Investigation of the purified nanocomplexes with CSI activity led to the additional conclusion that proteins of the glycolytic pathway such as glyceraldehyde-3-phosphate (GAPDH isoform Tdh3), enolase (Eno1), pyruvate decarboxylase (Pdc1) and pyruvate kinase (Pyk1) are also concentrated around the peak of CSI activity. The presence of these proteins in the pure chitosomes was further verified via testing for their individual enzymatic activities and by antibody studies. The relative levels of GAPDH, Pdc1 and Pyk1 were found to be higher in comparison to enolase; however GAPDH and Pdc1 proteins had a broad distribution across the purification gradient and were also found in neighboring fractions of peak of CSI activity. In addition to these, two high molecular weight proteins showing similarity to glucan synthase and fatty acid synthase were also found in such fractions as analyzed via MALDI-MS. In future it will be worthwhile to ascertain the active functional relationships among the different proteins found in chitosomal preparations using immuno fluorescence co-localization studies.
Subject Keywords: Chitin synthase; Yeast; chitosomal vesicles
Issue Date: 14-Nov-2005
Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB05 - E-Dissertationen

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