Recombinant Aspergillus terreus 3-ketoacyl-CoA reductase (ATEG_01423)

What are the optimal storage and handling conditions for Recombinant Aspergillus terreus 3-ketoacyl-CoA reductase?

For maintaining optimal enzyme activity and stability, several specific handling protocols should be followed:

For reconstitution of the lyophilized protein:

• Centrifuge the vial briefly before opening to bring contents to the bottom

• Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (50% is the default recommendation)

• Aliquot for long-term storage at -20°C/-80°C

These precise handling protocols ensure maximum retention of enzymatic activity for experimental applications.

How does Aspergillus terreus 3-ketoacyl-CoA reductase integrate with fungal metabolic pathways?

While the specific integration of 3-ketoacyl-CoA reductase in A. terreus metabolism has not been fully characterized, we can contextualize its role within the known metabolic framework of this organism. A. terreus exhibits sophisticated metabolic pathways, particularly for the production of organic acids like citrate and itaconic acid via the tricarboxylic acid (TCA) cycle .

The TCA cycle in A. terreus begins with the fusion of acetyl-CoA and oxaloacetate to form citrate, catalyzed by citrate synthase (CS) . The cycle continues through several enzymatic reactions involving aconitase (ACO), isocitrate dehydrogenase (ICDH), α-ketoglutarate dehydrogenase (KGDH), and other enzymes, ultimately regenerating oxaloacetate .

3-Ketoacyl-CoA reductase likely participates in fatty acid metabolism, which intersects with these central metabolic pathways through the common intermediate acetyl-CoA. The enzyme's activity in reducing 3-ketoacyl-CoA to 3-hydroxyacyl-CoA during fatty acid synthesis could influence acetyl-CoA availability for the TCA cycle and related pathways. This potential metabolic crosstalk suggests that 3-ketoacyl-CoA reductase may indirectly affect organic acid production, a commercially important process in A. terreus.

What role might Aspergillus terreus 3-ketoacyl-CoA reductase play in itaconic acid production?

Itaconic acid (itaconate) is an industrially valuable unsaturated C5-dicarboxylic acid produced by A. terreus at titers reaching 80 g/l under optimized fermentation conditions . The biosynthetic pathway for itaconate shares initial steps with citrate production but includes two additional enzymatic reactions .

The pathway proceeds as follows:

• Citrate is formed through the TCA cycle

• Citrate is converted to cis-aconitate by aconitase (ACO)

• cis-Aconitate is transported from the mitochondria to the cytosol

• cis-Aconitate is decarboxylated to itaconate by cis-aconitate decarboxylase (CAD)

• Itaconate is exported via a plasma membrane transporter (MFS)

While 3-ketoacyl-CoA reductase is not directly mentioned in the itaconic acid pathway, its role in fatty acid metabolism may indirectly influence itaconate production through several potential mechanisms:

Understanding these relationships could provide new targets for metabolic engineering strategies aimed at enhancing itaconic acid production.

How can structural and functional analysis of Aspergillus terreus 3-ketoacyl-CoA reductase inform metabolic engineering strategies?

Detailed structural and functional analysis of A. terreus 3-ketoacyl-CoA reductase can significantly advance metabolic engineering efforts in several ways:

• Structure-Function Relationships: Identifying catalytic domains and substrate binding sites would enable targeted mutagenesis to alter enzyme specificity or activity.

• Regulatory Mechanisms: Understanding how the enzyme is regulated could reveal potential control points for modulating fatty acid metabolism.

• Integration with Existing Engineering Approaches: Previous metabolic engineering studies in A. terreus have focused on overexpressing genes in the itaconate biosynthesis cluster (cadA, mtt, mfs) and modifying glycolytic enzymes like phosphofructokinase (PFK) . Knowledge of 3-ketoacyl-CoA reductase could complement these approaches.

• Novel Pathway Design: Comprehensive characterization could enable the design of novel biosynthetic pathways that leverage this enzyme's catalytic capabilities.

• Flux Redistribution: Modifying the enzyme's activity could potentially redirect carbon flux from fatty acid synthesis toward organic acid production, enhancing yields of valuable compounds.

The amino acid sequence provided in the product description can serve as a starting point for homology modeling and comparison with related enzymes, providing initial insights into the enzyme's structure and potential engineering targets.

What are the recommended protocols for expressing and purifying Recombinant Aspergillus terreus 3-ketoacyl-CoA reductase?

Based on the available product information, the following expression and purification protocol has proven successful:

Expression System and Conditions:

• Host: E. coli (likely BL21(DE3) or similar strain optimized for recombinant protein expression)

• Construct: Full-length protein (amino acids 1-353) with N-terminal His tag

• Expression conditions: Not explicitly stated, but standard protocols using IPTG induction in LB or similar rich media would be appropriate

Purification Strategy:

• Affinity Chromatography: Immobilized metal affinity chromatography (IMAC) using Ni-NTA or similar resin to capture the His-tagged protein

• Quality Control: SDS-PAGE analysis confirms >90% purity

• Buffer Exchange: Final protein in Tris/PBS-based buffer with 6% Trehalose, pH 8.0

• Processing: Lyophilization for stable storage and shipping

Researchers should note that while the product is supplied as a lyophilized powder, active enzyme preparations for experimental use should be carefully reconstituted following the recommended protocol to maintain enzymatic activity .

What experimental approaches can be used to study the enzymatic activity of Recombinant Aspergillus terreus 3-ketoacyl-CoA reductase?

Several complementary approaches can be employed to characterize the enzymatic activity of this reductase:

Spectrophotometric Assays:

• Monitor NADPH/NADH consumption at 340 nm, as the reduction of 3-ketoacyl-CoA likely requires these cofactors

• Establish reaction kinetics (Km, Vmax, kcat) using varying substrate concentrations

• Determine optimal reaction conditions (pH, temperature, ionic strength)

Chromatographic Analysis:

• High-Performance Liquid Chromatography (HPLC) to separate and quantify substrate depletion and product formation

• Liquid Chromatography-Mass Spectrometry (LC-MS) for detailed characterization of reaction products

Substrate Specificity Studies:

• Test activity with various chain lengths of 3-ketoacyl-CoA substrates

• Examine potential activity with alternative substrates

• Create a specificity profile using a substrate library

Inhibition Studies:

• Identify competitive and non-competitive inhibitors

• Determine inhibition constants (Ki)

• Use inhibitors as tools to probe the enzyme's active site

The experimental design should include appropriate positive and negative controls, and results should be validated using multiple methodological approaches to ensure reliability and reproducibility.

How can researchers investigate the potential interaction of Aspergillus terreus 3-ketoacyl-CoA reductase with other enzymes in metabolic pathways?

Investigating enzyme-enzyme interactions within metabolic pathways requires a multi-faceted approach:

In Vitro Interaction Studies:

• Pull-down Assays: Using the His-tagged recombinant protein as bait to identify interacting partners from A. terreus cell extracts

• Surface Plasmon Resonance (SPR): For quantitative measurement of binding kinetics between purified proteins

• Isothermal Titration Calorimetry (ITC): To determine thermodynamic parameters of protein-protein interactions

Metabolic Network Analysis:

• Flux Balance Analysis (FBA): Computational modeling to predict the effects of altering 3-ketoacyl-CoA reductase activity on metabolic flux distribution

• Metabolomics: Comprehensive analysis of metabolite changes when 3-ketoacyl-CoA reductase activity is modulated

• Stable Isotope Labeling: Tracing carbon flow through pathways using 13C-labeled substrates

Genetic Approaches:

• Gene Knockdown/Knockout: CRISPR-Cas9 or RNAi to reduce or eliminate 3-ketoacyl-CoA reductase expression and observe effects on related pathways

• Overexpression Studies: Similar to approaches used for other A. terreus enzymes , overexpression can reveal pathway bottlenecks

• Synthetic Biology: Reconstituting pathways with defined components to test functional interactions

These methodologies can reveal how 3-ketoacyl-CoA reductase integrates with other enzymes in A. terreus metabolism, potentially identifying new targets for metabolic engineering to enhance production of valuable compounds like itaconic acid.