Prokaryotic expression and bioactivity analysis of N-terminus domain of Pinellia ternata agglutinin using alkaline phosphatase signal peptide

From amino acid sequence to bioactivity: The biomedical potential of antitumor peptides

Chemoprevention is the use of natural and/or synthetic substances to block, reverse, or retard the process of carcinogenesis. In this field, the use of antitumor peptides is of interest as, (i) these molecules are small in size, (ii) they show good cell diffusion and permeability, (iii) they affect one or more specific molecular pathways involved in carcinogenesis, and (iv) they are not usually genotoxic. We have checked the Web of Science Database (23/11/2015) in order to collect papers reporting on bioactive peptide (1691 registers), which was further filtered searching terms such as "antiproliferative," "antitumoral," or "apoptosis" among others. Works reporting the amino acid sequence of an antiproliferative peptide were kept (60 registers), and this was complemented with the peptides included in CancerPPD, an extensive resource for antiproliferative peptides and proteins. Peptides were grouped according to one of the following mechanism of action: inhibition of cell migration, inhibition of tumor angiogenesis, antioxidative mechanisms, inhibition of gene transcription/cell proliferation, induction of apoptosis, disorganization of tubulin structure, cytotoxicity, or unknown mechanisms. The main mechanisms of action of those antiproliferative peptides with known amino acid sequences are presented and finally, their potential clinical usefulness and future challenges on their application is discussed.

Rhizoma Pinelliae trypsin inhibitor separation, purification and inhibitory activity on the proliferation of BGC-823 gastric adenocarcinoma cells

The aim of this study was to isolate and purify Rhizoma Pinelliae trypsin inhibitor (RPTI), determine its N-terminal amino acid sequence and evaluate its inhibitory effect on the proliferation of poorly differentiated BGC-823 human gastric adenocarcinoma cells. RPTI was separated and purified from a 40% (NH₄)₂SO₄ precipitate of crude protein extract of Pinellia ternata tuber using affinity chromatography with trypsin as the ligand. The N-terminal amino acid sequence of RPTI was determined using the Edman degradation method. The inhibitory effect of RPTI on BGC-823 cell proliferation was detected in vitro using the MTT method and in vivo in tumour-bearing mice. The purified RPTI showed a single band under SDS-PAGE, its molecular weight was 14 kDa and its N-terminal amino acid sequence was DPVVDG. RPTI inhibited trypsin activity, with an inhibition ratio of 1:6.78 (mass). RPTI significantly inhibited the proliferation of BGC-823 cells in vitro. The IC₅₀ of RPTI was 16.96 μg/ml within 48 h after treatment and 9.61 μg/ml within 72 h after treatment. Subcutaneous injection of RPTI around the tumour significantly inhibited BGC-823 tumour growth in mice. The tumour inhibitory effect was concentration- and dose-dependent. RPTI did not significantly influence the spleen coefficient of the mice. In conclusion, RPTI is a serine proteinase inhibitor with antitumour activity.

Purification of a mannose-binding lectin Pinellia ternata agglutinin and its induction of apoptosis in Bel-7404 cells

A novel high-throughput purification method for a monocot mannose-binding lectin, Pinellia ternata agglutinin (PTA), from tubers of P. ternata was established by mannose-Sephrose 4B affinity chromatography. The total protein was extracted from tubers of P. ternata using phosphate buffered saline (PBS) buffer. The extracted total protein was precipitated completely at 65% ammonium sulfate saturation and dissolved in different concentrations of NaCl solution to activate its binding affinity toward the column. PTA was bound to the affinity column by loading of the total protein into the column and elution using PBS buffer. The maximum purification yield (35.5mg/g) was obtained when PTA was treated with 25% (w/v) NaCl solution, and the purity of PTA analyzed by SDS-PAGE was ∼97%. The agglutination property of purified PTA was confirmed by mouse erythrocytes, which indicates its biological function. Nuclear staining assay and DNA fragmentation demonstrated that PTA could induce apoptosis of Bel-7404 cells, which further demonstrates its biological and pharmacological activities. Induction of apoptosis in the human tumor Bel-7404 cell line by PTA indicates its possible use in cancer therapy. The present investigation reports a significantly improved isolation method to obtain highly purified mannose-binding plant lectin proteins. The proposed method has great potential for industrial application because of its advantages, which include rapid isolation, high purity, high yield, low cost, and minimal requirement of chemical materials.