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Engineering Commons

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Theses/Dissertations

Chemical engineering

Biochemistry, Biophysics, and Structural Biology

1988

Articles 1 - 2 of 2

Full-Text Articles in Engineering

Characterization Of Substrate Binding And Catalytic Mechanisms Of An Endoxylanase, Amylosucrase, And Porcine Pancreatic Alpha-Amylase , Bernard Yi Tao Jan 1988

Characterization Of Substrate Binding And Catalytic Mechanisms Of An Endoxylanase, Amylosucrase, And Porcine Pancreatic Alpha-Amylase , Bernard Yi Tao

Retrospective Theses and Dissertations

The subsite affinity map of an endo-(1 → 4)-[beta]-xylanase produced by Aspergillus niger has been determined by using linear, [superscript]3H-reducing-end-labeled xylooligosaccharides ranging in length from xylotriose through xylooctaose. No evidence of multiple attack or of condensation and transxylosylation reactions was found. Bond cleavage frequencies were highest near the reducing end of short substrates, with the locus of highest frequencies moving towards the middle of larger substrates. This endoxylanase has five major subsites, with the catalytic site located between the third and fourth subsites, counting from the non-reducing end of the bound substrate. The subsite to the non-reducing ...


Mutagenesis Of The Active Site Of Glucoamylase From Aspergillus Awamori , Michael R. Sierks Jan 1988

Mutagenesis Of The Active Site Of Glucoamylase From Aspergillus Awamori , Michael R. Sierks

Retrospective Theses and Dissertations

The Aspergillus awamori glucoamylase gene was modified by cassette mutagenesis, and eleven mutated enzymes were expressed by Saccharomyces cerevisiae;Four mutations were constructed to change the essential Trp 120 residue in subsite 4 to Tyr, Phe, His, and Leu. All the mutations bound maltose (G2) and isomaltose (iG2) more strongly than wild-type glucoamylase. A subsite map of the Tyr 120 mutation showed significantly higher affinities for D-glucosyl residues in subsites 1 and 2, suggesting an interaction of Trp 120 with residues located there;Three carboxylic acid residues in the active site, Asp 176, Glu 179, and Glu 180, were mutated ...