C-Peptide (3-33), Human – Catalog #B2026671

C-Peptide (3-33), Human (Catalog #B2026671) is a fragment of human proinsulin-derived C-peptide supplied as 0.5 mg of lyophilized powder. The C-peptide is the connecting chain linking the A and B chains of insulin. During insulin synthesis and secretion, proinsulin is proteolytically cleaved to release equimolar amounts of insulin and C-peptide. Because C-peptide is not extracted by the liver on first pass (unlike insulin), plasma C-peptide levels directly reflect pancreatic beta-cell insulin secretion.

Scientific Overview

C-peptide is a 31-amino-acid peptide that links the A and B chains of insulin within the proinsulin molecule. Proinsulin undergoes proteolytic cleavage by endopeptidases to release mature insulin and C-peptide in a 1:1 molar ratio. Unlike insulin, C-peptide is not extracted by the liver during first-pass circulation, making its plasma concentration a faithful biomarker of pancreatic beta-cell secretion rate and function.

The C-peptide (3-33) fragment represents the physiologically active form used in many research applications. C-peptide itself has been shown to have biological effects independent of insulin, including roles in vasodilation, cellular signaling, and metabolic regulation.

Key applications include:

• Direct measurement of endogenous insulin secretion in diabetes diagnosis and classification
• Assessment of pancreatic beta-cell function and reserve
• Validation of metabolic assays and glucose homeostasis studies
• Research into C-peptide's independent biological effects on vascular and cellular function
• Use as a reference standard in immunoassays and bioanalytical methods

Usage & Handling Guidance

Store lyophilized powder at −20°C. Reconstitute in sterile, distilled water or phosphate-buffered saline (PBS) immediately before use. Prepare aliquots to minimize repeated freeze–thaw cycles, which can affect peptide integrity.

• Reconstitution: Dissolve in appropriate assay buffer; reconstitution concentration is assay-dependent. Request the COA/TDS for lot-specific information.
• Stability: In solution, C-peptide may aggregate or degrade over time. Use freshly prepared solutions when possible, or store at 2–8°C for short-term use.
• Purity and identity: Request available lot documentation (COA, HPLC trace) to confirm sequence and purity.

What You Get

• 0.5 mg of human C-peptide (3-33), supplied as lyophilized powder
• High-purity peptide fragment for research and assay development
• A stable marker of endogenous insulin secretion
• For research use only (RUO)

Why Researchers Choose It

• Direct reflection of pancreatic beta-cell insulin secretion (not hepatically extracted)
• Well-established biomarker in diabetes and metabolic research
• Stable during circulation, enabling accurate in vivo measurement
• Convenient lyophilized format for long-term storage
• Essential for distinguishing type 1 from type 2 diabetes and assessing beta-cell reserve

Frequently Asked Questions (FAQ)

• What is C-peptide and why is it important?
  C-peptide is the connecting chain cleaved from proinsulin when insulin is synthesized. Unlike insulin, it is not removed by the liver, so its plasma level directly reflects the rate of insulin secretion by beta cells.
• How does C-peptide (3-33) differ from full-length C-peptide?
  C-peptide (3-33) is the physiologically active form after proteolytic processing. It is the form measured clinically to assess endogenous insulin production.
• How should I reconstitute the peptide?
  Dissolve in sterile distilled water or PBS. The specific concentration depends on your assay. Request the COA/TDS for lot-specific guidance.
• Can this peptide be used in immunoassays?
  Yes. C-peptide is widely used as a reference standard in radioimmunoassay (RIA) and immunometric assays for measuring circulating C-peptide levels.
• How long is the lyophilized powder stable?
  At −20°C, lyophilized peptides are generally stable for years. Request available lot-specific stability data from the supplier.
• Is lot-specific documentation available?
  Yes. Request a quote or contact us for available COA, HPLC, and other analytical data for your lot.

References

• Faber OK, Binder C. C-peptide: an index of insulin secretion. Diabetes Metab Rev. 1986;2(3-4):331-45.
• Polonsky KS, Rubenstein AH. C-peptide as a measure of the secretion and hepatic extraction of insulin. Pitfalls and limitations. Diabetes. 1984;33(5):486-94.
• Jones AG, Hattersley AT. The clinical utility of C-peptide measurement in the care of patients with diabetes. Diabet Med. 2013;30(7):803-17.
• Fu Z, Gilbert ER, Liu D. Regulation of insulin synthesis and secretion and pancreatic Beta-cell dysfunction in diabetes. Curr Diabetes Rev. 2013;9(1):25-53.