Mutant PQQ-Dependent Glucose Dehydrogenase for Accurate Clinical Measurement
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Solution Overview
Problem
Current glucose determination methods using PQQ-dependent s-GDH face challenges due to the enzyme's broad substrate spectrum, which can lead to inaccurate results, especially in patients with high levels of other sugars like maltose, and existing mutants with improved specificity often compromise thermo stability.
Innovation Solution
A mutant PQQ-dependent s-GDH with lysine substitutions at positions 122 and/or 124, combined with other specific amino acid modifications, enhances both thermo stability and substrate specificity for glucose, reducing interference from other sugars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing mutants with improved substrate specificity are used, then measurement precision is improved, but thermo stability deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically modifying amino acid positions in the s-GDH protein structure. Specifically, it introduces lysine at position 122 and alanine at position 124, which are strategic parameter changes in the protein's primary structure that simultaneously improve both substrate specificity and thermo stability, resolving the contradiction between measurement precision and enzyme stability.
Solution Approach 2:
The patent applies local quality by making targeted amino acid substitutions at specific positions (122 and 124) rather than global modifications. These localized changes in the protein's active site region enhance glucose specificity while the overall protein structure maintains its thermo stability, allowing improved measurement precision without sacrificing enzyme stability.
2Stability of the object's composition
If wild-type s-GDH is used, then thermo stability is maintained, but measurement precision deteriorates due to broad substrate spectrum
Solution Approach 1:
The patent modifies the wild-type s-GDH by introducing specific amino acid changes at positions 122 and 124. These parameter changes in the protein sequence narrow the substrate spectrum to prefer glucose while preserving the overall structural integrity and thermo stability characteristics of the wild-type enzyme.
Solution Approach 2:
The patent applies local quality by making targeted amino acid substitutions at specific positions (122 and 124) in the protein structure. These localized modifications enhance glucose binding specificity without disrupting the global structural features that confer thermo stability to the wild-type enzyme.
3Measurement precision
If amino acid substitutions are made to improve substrate specificity, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by introducing only two specific amino acid substitutions (lysine at position 122 and alanine at position 124) rather than extensive modifications. This minimal parameter change approach achieves improved glucose specificity while keeping the protein structure relatively simple and easy to produce.
Solution Approach 2:
The patent applies partial action by making only the necessary minimum number of amino acid changes (two positions) to achieve improved glucose specificity. This partial modification approach suffices to resolve the substrate spectrum issue without introducing excessive complexity into the protein structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mutant s-GDH exhibits significantly improved thermo stability and specificity for glucose, minimizing interference from other sugars, thus providing accurate glucose measurements in clinical samples.
Implementation Method 1
PQQ-dependent glucose dehydrogenases (EC 1.1.5.2) catalyze a reaction in which glucose is oxidized to gluconolactone
Implementation Method 2
glucose is oxidized to gluconolactone
Implementation Method 3
A mutant PQQ-dependent s-GDH with lysine substitutions at positions 122 and/or 124, combined with other specific amino acid modifications, enhances both thermo stability and substrate specificity for glucose
Data Source
AI summary
The present invention relates to a mutant protein of PQQ-dependent s-GDH characterized in that in at least one of the positions 122 and 124 the amino acid lysine is present, wherein these positions correspond to the amino acid positions known from the A. calcoaceticus s-GDH wild-type sequence (SEQ ID NO: 2), it also discloses genes encoding such mutant s-GDH, and different applications of these s-GDH mutants, particularly for determining the concentration of glucose in a sample.