Related Experiment Video
Updated: Aug 7, 2026

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation
Published on: May 23, 2025
Cathepsin A-like activity is possibly the main acidic carboxypeptidase in human platelets
1Department of InstrumentalAnalysis, Medical Academy of Bialystok, Mickiewica 2, 15-230 Bialystok, Poland.
Abstract:
Human platelets were investigated for activity of the acidic carboxypeptidases: cathepsin A, lysosomal carboxypeptidase B and prolyl-carboxypeptidase. It was found that the main acidic carboxypeptidase in human platelets had cathepsin A activity. No activity of lysosomal carboxypeptidase B and prolyl-carboxypeptidase in human platelets was detectable using their specific substrates. Human platelet cathepsin A-type enzyme hydrolyzed at the highest rate Cbz-Phe-Ala, Cbz-Phe-Met and Cbz-Phe-Leu, did not require sulfhydryl activator and was inhibited by serine protease inhibitors (DFP, DCI) and inhibitors that react with the SH group (mersalyl acid, PCMS, PCMB, HgCl2). Cbz-Phe-Ala and Cbz-Glu-Tyr were hydrolyzed at a broad pH range with optimum at pH 5.0-6.0. The chromatographic analysis on Con A-Sepharose and DEAE-Sephacel showed different forms of Cbz-Phe-Ala-hydrolyzing enzyme in human platelets. The multiple forms of this enzyme were probably due to heterogeneity of carbohydrate moiety.
More Related Videos
07:13Characterizing Modulators of Protease-Activated Receptors with a Calcium Mobilization Assay Using a Plate Reader
Published on: May 24, 2024
08:56Demonstration of Proteolytic Activation of the Epithelial Sodium Channel (ENaC) by Combining Current Measurements with Detection of Cleavage Fragments
Published on: July 5, 2014
Related Concept Videos
Structure and Function of Platelets
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
Caspases
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Formation of the Platelet Plug
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
ATP Driven Pumps II: P-type Pumps
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...