Agile BioScience

C-terminal Sequencing

C-terminal Sequencing Services for Advanced Protein Characterization

Accurate protein C-terminal analysis using carboxypeptidase digestion and mass spectrometry for therapeutic proteins, recombinant proteins, and biopharmaceutical applications. Complete your structural understanding with definitive C-terminal data.

  • Expertise in protein C-terminal analysis
  • Dual-method approach: carboxypeptidase sequencing + mass spectrometry
  • Trusted CRO partner for global biopharma companies 
  • 500+ therapeutic protein C-terminal analysis projects completed
Request a Quote

Comprehensive C-terminal Sequencing Services

While the N-terminus of a protein gets much of the attention, the C-terminus holds equally critical secrets about your molecule’s integrity. Is the sequence complete, or are there unexpected truncations? Has post-translational processing occurred correctly? For therapeutic proteins, especially biosimilars, confirming C-terminal integrity is not just best practice—it’s a regulatory expectation.

C-terminal sequencing completes the picture of your protein’s primary structure. It verifies that the expressed protein matches the intended design from start to finish. Our specialized services provide the definitive data needed to confirm structural authenticity, identify heterogeneity, and ensure batch-to-batch consistency for your most valuable candidates.

We address the analytical challenges of C-terminal analysis with a strategic, multi-method approach tailored to your protein’s specific characteristics.

Our Core Methodologies 

Carboxypeptidase Sequencing: Controlled Enzymatic Analysis


This classical method uses enzymes called carboxypeptidases to sequentially cleave amino acids from the C-terminus. By controlling digestion time and analyzing the released amino acids, we can determine the sequence.

  • Ideal For: Proteins with free C-termini, shorter sequences, and situations where a time-course analysis is beneficial.
  • Key Advantage: Provides a direct, functional assessment of the C-terminal sequence under native-like conditions.
  • Application: Quality control for peptides and simpler recombinant proteins, verifying the absence of C-terminal extensions or truncations.

Mass Spectrometry C-terminal Sequencing: Precision for Complexity


Mass spectrometry has become the powerhouse for C-terminal sequencing, particularly for large, complex biologics. Techniques like LC-MS/MS can analyze the intact protein or specific peptides to pinpoint the exact C-terminal sequence and any modifications.

  • Ideal For: Large therapeutic proteins (like mAbs), proteins with blocked C-termini, and detecting low-level sequence variants or modifications.
  • Key Advantage: High sensitivity and specificity; can identify modifications like amidation or lysine clipping directly from the mass data.
  • Application: In-depth therapeutic protein C-terminal analysis for regulatory filings and troubleshooting production issues.

Recombinant Protein Structural Analysis


A complete structural verification requires confirming both ends of your protein. Our recombinant protein structural analysis service integrates C-terminal data with N-terminal sequencing and other techniques to provide a comprehensive certificate of analysis.

  • Ideal For: Final confirmation of clone fidelity, supporting IND/BLA applications, and demonstrating biosimilarity.
  • Key Advantage: Provides a complete picture of protein identity, essential for regulatory confidence and process validation.
  • Application: Critical for biopharmaceutical protein characterization packages for novel therapeutics and biosimilars.

Why Partner With Us? Your Trusted C-terminal Sequencing CRO

C-terminal analysis is technically demanding. You need a partner with proven expertise and the right tools to deliver reliable, defensible data.

  • End-to-End Biopharmaceutical Characterization: We don’t just perform a test; we provide context. Our reports integrate C-terminal findings into the bigger picture of your protein’s structure, offering insights that support process development and regulatory strategy.
  • Dual-Expertise Strategy: There is no one-size-fits-all solution for C-terminal sequencing. Our scientists excel in both enzymatic and MS-based methods, allowing us to select and validate the optimal approach for your specific molecule, ensuring the highest quality results.
  • Regulatory-Compliant Documentation: As a trusted protein sequencing service CRO, we understand what regulators need to see. Our deliverables are designed for submission, with complete method descriptions, raw data, and clear interpretations that stand up to scrutiny.
  • Deep Therapeutic Protein Experience: We have successfully characterized hundreds of molecules, including monoclonal antibodies, fusion proteins, enzymes, and biosimilars. This experience means we understand the common—and uncommon—C-terminal challenges you may face.
  • A Partner for the Global Stage: We serve clients worldwide, from virtual biotechs to large pharma, delivering the same level of quality, communication, and reliability expected by the industry’s leaders.

Characterization

Contact us

Error: Contact form not found.

Who We Serve: Ensuring Structural Fidelity Across the Industry

Our services are essential for organizations where structural verification is critical to success:

  • Biopharmaceutical Companies developing novel therapeutic proteins and biosimilars.
  • Biotechnology Startups needing robust characterization data for investor due diligence and IND enabling studies.
  • CROs and CDMOs seeking a specialized partner to extend their analytical service offerings.
  • Gene Therapy and Biosimilar Developers for whom demonstrating structural identity is a key regulatory hurdle.
  • Academic and Structural Biology Labs conducting detailed protein structure-function research.
Request a Quote

Applications of C-terminal Sequencing in Biopharma

C-terminal sequencing provides critical answers throughout the biopharmaceutical development lifecycle:

Therapeutic Protein C-terminal Analysis


Confirming the integrity of your lead candidate is paramount. Our therapeutic protein C-terminal analysis detects truncations, extensions, and sequence variants that could impact safety, efficacy, or stability, de-risking your development program.

Recombinant Protein Structural Analysis


Did your expression system produce the exact protein you designed? Recombinant protein structural analysis that includes C-terminal sequencing provides definitive proof, ensuring your clone is correct and your process is controlled.

Biopharmaceutical Protein Characterization for Regulatory Compliance


A complete characterization package for a BLA or biosimilar application must include C-terminal data. Our services provide the evidence required to satisfy regulators that your product’s primary structure is correct and consistent.

Outsourced Expertise as Your Protein Sequencing Service CRO


Not every organization has this specialized capability in-house. As a dedicated protein sequencing service CRO, we act as your seamless, expert partner, providing high-quality data without the capital investment in specialized equipment and expertise.

.

Carboxypeptidase Sequencing vs. Mass Spectrometry: Selecting the Optimal Method

Analytical Aspect

Carboxypeptidase Sequencing

Mass Spectrometry C-terminal Sequencing

Method Principle

Enzymatic digestion with time-course analysis of released amino acids.

High-resolution mass analysis of intact protein or enzymatically derived C-terminal peptide.

Best For

Proteins with free C-termini; direct functional analysis; simpler protein constructs.

Large, complex proteins (mAbs); high sensitivity requirements; detection of post-translational modifications (PTMs).

Information Obtained

Sequential order of amino acids from the C-terminus.

Exact molecular weight and fragmentation data to deduce the sequence and identify modifications.

Key Considerations

Enzyme specificity must be considered; can be slower.

Requires high-purity samples and expert data interpretation; higher instrumentation cost.

Role in Biopharma

Useful for specific QC applications and peptide analysis.

The gold-standard for regulatory-compliant therapeutic protein C-terminal analysis.

FAQ About C-terminal Sequencing

Q1. What is C-terminal sequencing used for?


C-terminal sequencing is used to determine the amino acid sequence at the end (C-terminus) of a protein. Its primary applications include verifying that a recombinant protein is fully and correctly expressed, detecting truncations or extensions that may occur during production, and confirming structural identity for biosimilars. It is a critical component of a complete protein characterization package.

Q2. How does carboxypeptidase sequencing work?


Carboxypeptidase sequencing works by incubating a purified protein with carboxypeptidase enzymes. These enzymes selectively cleave amino acids one at a time from the C-terminus. By taking samples at different time points and analyzing the released amino acids, we can deduce the sequence in which they were released, revealing the C-terminal order.

Q3.When should I use mass spectrometry C-terminal sequencing?


Mass spectrometry C-terminal sequencing is the preferred method for most therapeutic proteins, especially large molecules like monoclonal antibodies. It is particularly advantageous when you need high sensitivity, when dealing with complex mixtures, or when you suspect post-translational modifications (like amidation or glycosylation) near the C-terminus. It is the standard for regulatory submissions.

Q4.Can C-terminal sequencing detect protein modifications or truncations?


Yes, absolutely. This is one of its key strengths. Mass spectrometry can directly detect mass changes associated with modifications. Both enzymatic and MS methods can indicate truncations—either by revealing a shorter-than-expected sequence or by identifying a peptide that does not match the expected C-terminal end.

Q5.Are C-terminal sequencing results required for FDA/EMA regulatory submissions?


While not always explicitly stated as a standalone “test,” demonstrating the correctness of the primary structure, which includes the C-terminal sequence, is a fundamental requirement for characterizing a therapeutic protein. For original biologics and especially for biosimilars, C-terminal sequencing data is a standard and expected part of the analytical data package to prove identity and purity. Its absence would be a significant regulatory risk.

Characterization

Contact us

Error: Contact form not found.