Diagnostic Enzyme & IVD Assay Services
Transaminase Assay Enzyme Solutions
Develop and qualify ALT/AST transaminase activity methods with defined units, controlled reaction conditions, and documented QC for diagnostic and research use.
What Transaminase Assay Solutions Cover
Transaminases such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are routinely measured as markers of hepatocellular status, and their activity is a core readout in liver injury models and diagnostic panels. Our service develops and qualifies enzyme activity methods that quantify this catalytic activity rather than protein mass, so results reflect function under defined reaction conditions.
Engagements are scoped case by case. We adapt the assay format, sample type, and validation depth to your intended application, then document the units, reaction conditions, and calculations so the method can be reproduced and transferred.
Coupled Transamination Chemistry
The assay links the transamination reaction to a measurable optical signal. In the ALT/GPT format, alanine and alpha-ketoglutarate are converted to pyruvate and glutamate; pyruvate is then reduced by lactate dehydrogenase with oxidation of NADH to NAD+, and the rate of NADH disappearance is read at 340 nm. The AST/GOT format applies the same principle with aspartate as the amino donor and malate dehydrogenase as the coupling enzyme.
- Amino donor plus alpha-ketoglutarate as the core reaction pair
- Coupling enzyme: LDH for ALT, MDH for AST
- NADH oxidation monitored at 340 nm
Kinetic and Endpoint Options
Methods can be configured as continuous (kinetic) measurements that follow NADH disappearance over time, or as fixed-time (endpoint) measurements where the signal change is read after a defined incubation. Kinetic formats are commonly used when reaction-rate information is needed; endpoint formats are often chosen for higher-throughput or plate-based workflows.
- Continuous kinetic monitoring of NADH oxidation
- Fixed-time endpoint colorimetric detection
- Format selected against your sample volume and throughput needs
Sample-Tailored Preparation
Sample preparation is matched to the matrix. Serum and plasma are handled with attention to hemolysis and other interferences, while tissue and cell lysates are prepared in appropriate buffers with protease inhibitors and normalized by protein concentration so activity can be expressed per milligram of protein.
- Serum and plasma for clinical-style activity readouts
- Tissue and cell lysates for model and mechanistic work
- Protein normalization for U/mg reporting
| Parameter | Typical project scope | How it is defined | Documentation |
|---|---|---|---|
| Analyte | ALT, AST, or both, as scoped | Selected against your diagnostic or research question | Analyte definition and reaction scheme |
| Assay format | Kinetic or endpoint, as scoped | Chosen for throughput, sample volume, and rate information needs | Format rationale and read settings |
| Sample type | Serum, plasma, tissue or cell lysate | Matched to your study or panel design | Preparation and handling notes |
| Reaction conditions | Amino donor, alpha-ketoglutarate, NADH, coupling enzyme | Concentrations and order of addition defined during development | Reagent list and reaction setup |
| Detection | Spectrophotometric NADH monitoring at 340 nm | Wavelength and read interval set for the chosen format | Detection parameters and instrument notes |
| Activity units | U/L or U/mg protein, as scoped | The calculation is based on the NADH extinction coefficient and, where relevant, on protein concentration. | Worked calculation and unit definition |
| QC checks | Linearity, reproducibility, interference testing | Depth scoped to the intended use of the method | QC summary and acceptance criteria |
| Controls | No-substrate and no-sample negative controls; calibrator or standard curve where applicable | No-substrate and no-sample negative controls are run alongside a calibrator or standard curve where applicable. | Control design and expected behavior |
How an Engagement Works
Each project moves through a defined sequence from scoping to documentation, so the method you receive is reproducible and ready for your intended application.
Scope and Feasibility Review
We review your analyte, sample matrix, expected activity range, and intended use, then agree on the assay format, sample numbers, and validation depth for the project.
Sample and Reagent Preparation
Samples are prepared according to matrix, with appropriate buffers and protease inhibitors for lysates and attention to hemolysis and other interferences for serum or plasma. Reaction reagents include the amino donor, alpha-ketoglutarate, NADH, and the coupling enzyme.
Reaction Setup and Initiation
The reaction cocktail is assembled and the reaction is initiated by adding sample or substrate, following the order of addition defined during development. Negative controls without substrate or without sample are included alongside the test reactions.
Detection and Data Capture
NADH oxidation is followed by continuous spectrophotometric monitoring at 340 nm for kinetic formats, or read after a fixed incubation for endpoint formats. Raw signal data are captured with the read parameters recorded.
Customization Options
Transaminase methods are rarely one-size-fits-all. The options below describe what can be adapted during development so the final method fits your samples, instrument, and reporting needs.
Sample-Specific Handling
Preparation and dilution schemes are adapted to serum, plasma, or tissue and cell lysates, including protein normalization for lysate-based reporting.
- Serum and plasma handling with interference awareness
- Lysate preparation with protease inhibitors
- Dilution schemes matched to expected activity range
Kinetic or Endpoint Design
The readout format is selected against your throughput and information needs, with read intervals and incubation settings defined accordingly.
- Continuous 340 nm monitoring for rate data
- Fixed-time endpoint for plate-based workflows
- Read parameters recorded in the method file
Reagent and Coupling Configuration
Amino donor, alpha-ketoglutarate, NADH, and coupling enzyme levels are set during development, and reagent stability and storage conditions are documented for the working reagents.
- LDH coupling for ALT and MDH coupling for AST
- Reagent stability and storage notes
- Order of addition defined and recorded
Deliverables and Documentation
Deliverables are defined in the project scope of work. The table below shows the documentation types typically included when a transaminase activity method is developed and qualified.
Where a specific quantity or acceptance threshold is not fixed in advance, it is agreed during scoping and recorded in the final report.
| Deliverable | Description | Scope basis | Format |
|---|---|---|---|
| Method summary | Reaction scheme, reagent list, and step-by-step procedure | Defined at project start | Written method document |
| Unit definition and calculation | Activity units are reported with the worked calculation using the NADH extinction coefficient and protein concentration where applicable. | Agreed during scoping | Calculation sheet |
| QC summary | Linearity, reproducibility, and interference results with acceptance criteria | Depth as scoped | QC report |
| Control results | Outcomes are reported for no-substrate and no-sample negative controls, plus a calibrator or standard curve where applicable. | As scoped | Data tables |
| Raw data package | Signal traces or endpoint reads with read parameters | As scoped | Instrument export files |
| Transfer notes | Reagent stability and storage conditions, plus setup notes to support method transfer | As scoped | Transfer document |
Why Teams Choose This Service
Transaminase activity is a functional readout, and the value of the data depends on controlled reaction conditions and clear documentation. The points below describe how we approach that requirement.
Mechanism-Anchored Design
Methods are built on the coupled transamination reaction, so the readout directly reflects aminotransferase activity rather than protein abundance.
- Amino donor plus alpha-ketoglutarate reaction core
- Coupling enzyme and NADH detection defined explicitly
- Activity expressed in U/L or U/mg protein
Controls and Interference Awareness
Negative controls and interference checks are part of the method design, which helps distinguish true activity signal from matrix effects such as hemolysis.
- No-substrate and no-sample controls
- Hemolysis and interference testing as scoped
- Calibrator or standard curve where applicable
Documentation for Reproducibility
Reaction conditions, reagent stability and storage, and the activity calculation are documented so the method can be reproduced and transferred to your laboratory.
- Reagent stability and storage conditions recorded
- Worked calculation included
- Setup notes to support transfer
Applications and Context
Transaminase activity measurements are widely used in liver injury models and diagnostic panels, where ALT and AST serve as accessible markers of hepatocellular status. The table below places common applications alongside the assay considerations they typically raise.
Application-specific requirements are confirmed during scoping, since sample type and expected activity range influence the method design.
| Application | Typical sample | Assay consideration | Reporting focus |
|---|---|---|---|
| Liver injury model readout | Serum or plasma | Expected activity range may be elevated relative to control | Activity units with control comparison |
| Cell-based mechanistic studies | Cell lysate | Protein normalization needed for consistent reporting | U/mg protein |
| Tissue-based studies | Tissue lysate | Homogenization and buffer conditions affect recovery | U/mg protein with preparation notes |
| Diagnostic panel development | Serum or plasma | Interference testing and linearity are central to method qualification | U/L with QC summary |
Reagent Handling and Stability
Working reagents for coupled transaminase assays, including NADH and the coupling enzyme, are sensitive to handling and storage conditions. Reagent stability and storage conditions are documented as part of the method so that day-to-day performance remains consistent.
Where a project requires it, we can include reagent stability observations in the method documentation to support routine use after transfer.
Getting Started
To begin, share your analyte of interest, sample matrix, expected activity range, and intended use. We will review feasibility and propose an assay format, sample plan, and validation depth for your project.
Scope, sample numbers, and validation depth are agreed in the project scope of work after consultation, so the method matches your application rather than a fixed template.
FAQ
How does a transaminase activity assay differ from an antibody-based enzyme detection method?
A transaminase activity assay measures catalytic function through the coupled reaction between an amino donor and alpha-ketoglutarate, with NADH oxidation read at 340 nm. Antibody-based detection measures protein mass through binding rather than activity, so the two approaches answer different questions and are not interchangeable.
Which sample types can be used?
Serum, plasma, and tissue or cell lysates are all commonly used. Preparation is adapted to the matrix, with attention to hemolysis and other interferences in blood-derived samples and protein normalization for lysate-based reporting in U/mg protein.
Should the method be kinetic or endpoint?
Kinetic formats follow NADH disappearance continuously and are often chosen when reaction-rate information is needed, while endpoint formats read the signal after a fixed incubation and suit higher-throughput plate workflows. The choice is made during scoping against your sample volume and throughput needs.
How is enzyme activity calculated and reported?
Activity is calculated from the change in NADH signal using its extinction coefficient, and expressed as U/L for liquid samples or U/mg protein when protein normalization applies. The worked calculation and unit definition are included in the method documentation.
What QC is included?
QC typically covers linearity, reproducibility, and interference testing, alongside negative controls without substrate or without sample and a calibrator or standard curve where applicable. The depth of QC is agreed during scoping based on the intended use of the method.
Can the method be transferred to our laboratory?
Yes. Reaction conditions, reagent stability and storage notes, and the activity calculation are documented so the method can be reproduced and transferred. Transfer support is scoped in the project agreement.
References
- Zeng Y, Pan QB, Shen YX, et al. [Neutralization of interleukin-6 alleviates acute liver injury in mice]. Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology. 2020;28(6):509-514. View on PubMed
- Feng X, Hong S, Zhao H, et al. Biocatalytic cascade to polysaccharide amination. Biotechnology for biofuels and bioproducts. 2024;17(1):34. View on PubMed
Scope Your Transaminase Assay Method
Share your analyte, sample matrix, and intended use, and we will outline an assay format, sample plan, and validation depth for your project.