Recombinant Microbial Cells for Melatonin Production
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Solution Overview
Problem
Current methods for producing melatonin and related compounds in recombinant microorganisms are inefficient, despite advances in biosynthetic pathways, as they require exogenous cofactors and enzymes, limiting their cost-effectiveness and scalability.
Innovation Solution
Development of recombinant microbial cells expressing variants of E. coli GTP cyclohydrolase I (GCH1) and tryptohan hydroxylase (TPH) with specific mutations, which enhance monooxygenase activity, allowing for the production of oxidation products like 5HTP without the need for exogenous nucleic acids encoding dihydropteridine reductase or dihydromonapterin reductase, utilizing native bacterial compounds to support enzyme activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exogenous cofactors and enzymes are used in recombinant microorganisms for melatonin production, then the biosynthetic pathway can function, but the production efficiency remains low and costs increase
Solution Approach 1:
The patent enables the recombinant microorganism to produce its own required cofactors (BH4 and MH4) through endogenous enzymes (GCH1, PTS, SRP, PCD, DHPR) already present in the host cell, eliminating the need for exogenous supplementation and reducing production complexity
Solution Approach 2:
The patent introduces specific mutations in the GCH1 enzyme (e.g., T198I, D97V, M99I) to optimize its catalytic activity and substrate affinity, thereby improving the efficiency of endogenous BH4 production and overall melatonin synthesis pathway
2Reliability
If multiple exogenous enzymes are introduced into recombinant cells, then the complete biosynthetic pathway is established, but the process complexity and cost increase
Solution Approach 1:
The patent extracts and utilizes only the essential endogenous enzymes (GCH1, PTS, SRP, PCD, DHPR) required for cofactor synthesis, removing the need for other exogenous enzymes and simplifying the overall system while maintaining pathway completeness
Solution Approach 2:
The patent demonstrates that the endogenous GCH1 enzyme system can serve multiple functions: producing BH4 for TPH activity, producing MH4 for phenylalanine hydroxylase activity, and supporting overall cell metabolism, thereby reducing the need for specialized exogenous enzymes
3Productivity
If native E. coli GCH1 is used, then the cell maintains normal metabolic function, but the hydroxylation activity of TPH is insufficient for efficient melatonin production
Solution Approach 1:
The patent introduces specific amino acid mutations in GCH1 (T198I, D97V, M99I) to change the enzyme's catalytic parameters, including substrate binding affinity and turnover rate, thereby enhancing TPH hydroxylation activity while maintaining enzyme stability
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 approach results in a significant increase in melatonin and related compound production, achieving a 10-fold increase in 5HTP production and improved hydroxylation activity, reducing the reliance on exogenous cofactors and enzymes, thereby simplifying and cost-reducing the production process.
Implementation Method 1
GTP cyclohydrolase I (GCH1)...can be biosynthesized from endogenous GTP via a pathway comprising a GTP cyclohydrolase I (GCH1)
Implementation Method 2
TPH and many other mammalian aromatic amino acid hydroxylases require oxygen and tetrahydropterin (BH4) as cofactors
Implementation Method 3
regenerated into BH4 via consecutive reactions by pterin-4a-carbolamine dehydratase (PCD)
Implementation Method 4
regenerated into BH4 via consecutive reactions by pterin-4a-carbolamine dehydratase (PCD) and dihydropterin reductase (DHPR)
Implementation Method 5
variants of E. coli GTP cyclohydrolase I (GCH1)...provides for an increased hydroxylation activity
Implementation Method 6
The first step is this pathway, the conversion of L-tryptophan to 5HTP, is catalyzed by L-tryptophan hydroxylase (TPH)
Data Source
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AI summary
Described herein are recombinant microbial host cells comprising biosynthetic pathways and their use in producing oxidation products and downstream products, e.g., melatonin and related compounds, as well as enzyme variants, nucleic acids, vectors and methods useful for preparing and using such cells. In specific aspects, the present invention relates to monooxygenases, e.g., amino acid hydroxylases, with a modified cofactor-dependency, and to enzyme variants and microbial cells providing for an improved supply of cofactors.