GD4K-na peptide

• Handling and Storage of Synthetic Peptides
• Material Safety Data Sheets (MSDS)

Batch to batch variation of the purity

The GD4K-na peptide, Gly-Asp-Asp-Asp-Asp-Lys-β-naphthylamide, is a synthetic substrate designed for studying the enzymatic activity of enteropeptidase. This peptide mimics the natural trypsinogen activation sequence (Asp)₄-Lys, which is specifically cleaved by enteropeptidase. Kinetic studies reveal that GD4K-na is efficiently hydrolyzed by the recombinant human enteropeptidase light chain (L-HEP), exhibiting a K_m of 0.16 mM and a k_cat of 115 s⁻¹. The high specificity and catalytic efficiency of L-HEP toward GD4K-na highlight its role in substrate recognition and cleavage, making it a valuable tool for probing enteropeptidase function.

The enzymatic cleavage of GD4K-na by L-HEP is characterized by a k_cat/K_m ratio of 718.7 mM⁻¹ s⁻¹, significantly higher than that observed for the bovine enteropeptidase light chain. This difference is attributed to structural variations in the substrate-binding region, particularly the K96R substitution in L-HEP, which enhances substrate affinity. The peptide's β-naphthylamide moiety allows for sensitive fluorescence-based detection of cleavage, facilitating kinetic analyses. These properties make GD4K-na a robust substrate for investigating enteropeptidase kinetics and mechanism.

• Gasparian ME, Ostapchenko VG, Schulga AA, Dolgikh DA, Kirpichnikov MP. Expression, purification, and characterization of human enteropeptidase catalytic subunit in Escherichia coli. Protein Expr Purif. 2003 Sep;31(1):133-9. doi: 10.1016/s1046-5928(03)00159-1. PMID: 12963350.

Trifluoroacetic acid (TFA) is a common counterion from the purification process using High-Performance Liquid Chromatography (HPLC). The presence of TFA can affect the peptide's net weight, appearance, and solubility.

Impact on Net Weight: The TFA salt contributes to the total mass of the product. In most cases, the peptide content constitutes >80% of the total weight, with TFA accounting for the remainder.

Solubility: TFA salts generally enhance the solubility of peptides in aqueous solutions.

In Biological Assays: For most standard in vitro assays, the residual TFA levels do not cause interference. However, for highly sensitive cellular or biochemical studies, please be aware of its presence.