Rational and Evolutive Reengineering of Phosphatase: from Method Development to Understanding of Properties

  • The thesis focuses on directed evolution and structure function relationship of phytase from Yersinia mollaretii (Ymphytase). The “key beneficial” mutations identified in the directed evolution have been iteratively combined. Ymphytase variant with 54% improvement in thermostability (58°C for 20 min) and 200 U/mg improved activity was achieved. MD simulations results showed decreased overall Ymphytase flexibility in thermostable variant with slight increase in active site loop flexibility. The decreased flexibility might be due to improved intra-protein interactions like hydrogen bonds (G187S, K289E) and salt-bridge interaction (T77K). Three conceptually novel methods for protein engineering have been developed in part-III (Chapter 6 – 8). Combinatorial assembly of site saturation test in protein segment (ProCASTing), a sequence independent method was developed for parallel site saturation of more than one consecutive site (4 to 8) in any part of the protein. Multisite combinatorial assembly of site saturation test (OmniCASTing), practically simple method was developed for parallel site saturation of more than one site (five) regardless of positions in the gene. Using OmniCASTing, a variant with improved thermostability, pH stability and activity was obtained. Three properties improvement might be due to cooperative effects between the new combinations of mutations compare to parent combination. Protein consensus based surface engineering (ProCoS) method combining computational analysis and molecular biology tools was developed. The utility of ProCoS method has been demonstrated by surface engineering of Ymphytase that yielded a variant with 34 amino acid substitution (20% negative polar amino acids) and 3.8 fold improvement in pH stability (pH 2.8). Two hypotheses have been proposed in part-IV (chapter 8 – 9) and validated by experimental evidences.

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Publishing Institution:IRC-Library, Information Resource Center der Jacobs University Bremen
Granting Institution:Jacobs Univ.
Author:Amol Vaijanathappa Shivange
Referee:Ulrich Schwaneberg, Danilo Roccatano, Stefan Haefner
Advisor:Ulrich Schwaneberg
Persistent Identifier (URN):urn:nbn:de:gbv:579-opus-1005406
Document Type:PhD Thesis
Language:English
Date of Successful Oral Defense:2010/12/16
Date of First Publication:2020/03/04
PhD Degree:Biochemical Engineering
School:SES School of Engineering and Science
Library of Congress Classification:T Technology / TP Chemical technology / TP248.13-248.65 Biotechnology / TP248.3 Biochemical engineering. Bioprocess engineering
Call No:Thesis 2010/43

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