Alternative Carboxylating Enzymes for Carbon Fixation
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Solution Overview
Problem
The productivity of the Calvin-Benson Cycle in carbon fixation is limited by the slow rate and lack of substrate specificity of the carboxylating enzyme Rubisco, making it difficult to enhance carbon fixation rates in plants.
Innovation Solution
Development of alternative carbon fixation pathways using enzymes such as PEP carboxylase, pyruvate carboxylase, and acetyl-CoA carboxylase, which catalyze carboxylation reactions to produce oxaloacetate and malonyl-CoA, with glyoxylate or pyruvate as export products, to enhance carbon fixation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Calvin-Benson Cycle is used for carbon fixation, then carbon fixation occurs in plants, but the rate is limited by the slow turnover of Rubisco enzyme
Solution Approach 1:
The patent changes the enzymatic parameters by substituting Rubisco with alternative carboxylating enzymes (PEP carboxylase, pyruvate carboxylase, acetyl-CoA carboxylase) that have different kinetic properties, including higher turnover rates and improved substrate specificity, thereby resolving the contradiction between carbon fixation productivity and enzyme speed
Solution Approach 2:
The patent introduces intermediary metabolites (oxaloacetate, malonyl-CoA) as products of alternative carboxylation pathways that can be converted to glyceraldehyde-3-phosphate, serving as mediators between inorganic carbon and the Calvin-Benson Cycle, thus bypassing the rate-limiting Rubisco step while maintaining carbon fixation productivity
2Productivity
If Rubisco enzyme is used for carboxylation, then carbon fixation occurs, but substrate specificity is lacking leading to photorespiration
Solution Approach 1:
The patent changes the specificity parameter by selecting alternative carboxylating enzymes that exhibit higher CO2 specificity and lower oxygenase activity compared to Rubisco, thereby improving carbon fixation efficiency while reducing photorespiratory losses through enhanced substrate discrimination
Solution Approach 2:
The patent segments the carbon fixation function from Rubisco by assigning carboxylation to alternative enzymes with superior substrate specificity, separating the carboxylation step from the subsequent Calvin-Benson Cycle steps, thereby allowing optimization of each function independently
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
These alternative pathways demonstrate higher pathway specific activities and energetic efficiency, potentially overcoming the limitations of the natural Calvin-Benson Cycle by increasing carbon fixation rates and reducing energetic costs.
Implementation Method 1
enzymes which catalyze reactions of a carbon fixation pathway, wherein at least one of the reactions of the carbon fixation pathway is a carboxylation reaction
Implementation Method 2
an enzyme which performs the carboxylation reaction is selected from the group consisting of phophoenolpyruvate (PEP) carboxylase, pyruvate carboxylase and acetyl-CoA carboxylase
Data Source
AI summary
A system for carbon fixation is provided. The system comprises enzymes which catalyze reactions of a carbon fixation pathway, wherein at least one of the reactions of the carbon fixation pathway is a carboxylation reaction, wherein products of the reactions of the carbon fixation pathway comprise oxaloacetate and malonyl-CoA, wherein an enzyme which performs the carboxylation reaction is selected from the group consisting of phophoenolpyruvate (PEP) carboxlase, pyruvate carboxylase and acetyl-CoA carboxylase and wherein an export product of the carbon fixation pathway is glyoxylate. Additional carbon fixation pathways are also provided and methods of generating same.