Bradykinin is a nine-residue endogenous kinin and a principal agonist of the bradykinin B2 receptor. Its sequence, Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg (RPPGFSPFR), is generated from kininogen precursors through the kallikrein–kinin system and participates in acute vascular, nociceptive and inflammatory signaling.

Because Bradykinin produces rapid and transient responses and is readily metabolized by peptidases, it is particularly useful for studying short-timescale GPCR signaling, endothelial responses and the transition from intact kinins to their bioactive metabolites.

Product Information

Bradykinin Primarily Activates the B2 Kinin Receptor

Intact Bradykinin is a physiological ligand of the B2 receptor, a rhodopsin-family G protein-coupled receptor that is broadly expressed in vascular, sensory and other tissues.

B2 receptor activation can couple through G_q-family signaling to phospholipase C, phosphoinositide turnover and intracellular Ca²⁺ mobilization. Depending on cell type, kinin signaling can also influence nitric oxide, prostaglandin and MAP kinase pathways.

For receptor-specific experiments, intact Bradykinin should be distinguished from des-Arg9-Bradykinin. Removal of the C-terminal Arg shifts ligand preference toward the inflammation-inducible B1 receptor rather than simply producing a shorter equivalent of Bradykinin.

Acute Kinin Signaling and Nociception

Bradykinin is generated rapidly during tissue injury and can activate peripheral sensory pathways while also increasing vascular permeability and altering vascular tone. These properties have made it a useful experimental mediator for studying inflammatory hyperalgesia and neurovascular coupling.

The biological response is strongly context-dependent. B2 receptors contribute prominently to the effects of intact Bradykinin under many basal and acute conditions, while B1 receptor expression can increase substantially after inflammatory stimulation or tissue damage.

We recommend identifying the exact ligand and receptor subtype when interpreting kinin experiments rather than treating B1 and B2 signaling as interchangeable.

Bradykinin Metabolism Changes Receptor Pharmacology

Peptide degradation is part of Bradykinin biology rather than simply an analytical limitation. Carboxypeptidase removal of the terminal Arg generates des-Arg9-Bradykinin, changing receptor preference toward B1.

Other proteases, including angiotensin-converting enzyme and additional kininases, further regulate the duration of intact Bradykinin signaling. Incubation time and protease activity can therefore alter the molecular species present during an experiment.

Salt Form and Concentration Calculations

The molecular weight of approximately 1060.22 Da describes the Bradykinin peptide moiety. CAS 5979-11-3 is associated with Bradykinin triacetate, for which the reference 1:3 acetate composition has a molecular weight of approximately 1240.38 Da.

For quantitative experiments, we recommend using lot-specific peptide content and counterion information when preparing molar solutions. Nominal lyophilized mass should not automatically be treated as 100% peptide mass.

Research Applications

Bradykinin can support B2 receptor pharmacology, Ca²⁺ signaling, endothelial nitric oxide studies, vascular-permeability experiments, nociception models, kallikrein–kinin pathway research and investigations of peptide degradation.

Related neuroactive ligands can be explored in our Pain and Inflammation Modulation Peptides collection.

Defined kinin analogs, truncations and receptor-directed sequence variants can also be evaluated through Chemical Peptide Synthesis.

Frequently Asked Questions

Does intact Bradykinin primarily activate B1 or B2 receptors?

Intact Bradykinin is primarily a B2 receptor agonist. The metabolite des-Arg9-Bradykinin preferentially activates the B1 receptor.

What is the molecular weight of Bradykinin?

The Bradykinin peptide moiety has a molecular weight of approximately 1060.22 Da. Counterion-containing material has a higher total formula weight.

Why is CAS 5979-11-3 associated with a higher molecular weight?

CAS 5979-11-3 corresponds to Bradykinin triacetate. Its reference composition includes three acetate molecules in addition to the peptide.

Research Use Only.