A Novel Bradykinin-Related Peptide, RVA-Thr6-BK, from the Skin Secretion of the Hejiang Frog; Ordorrana hejiangensis: Effects of Mammalian Isolated Smooth Muscle

Discovery and analysis of a novel antimicrobial peptide B1AW from the skin secretion of Amolops wuyiensis and improving the membrane-binding affinity through the construction of the lysine-introduced analogue

In the development and study of antimicrobial peptides (AMPs), researchers have kept a watchful eye on peptides from the brevinin family because of their extensive antimicrobial activities and anticancer potency. In this study, a novel brevinin peptide was isolated from the skin secretions of the Wuyi torrent frog, Amolops wuyiensis (A. wuyiensisi), named B1AW (FLPLLAGLAANFLPQIICKIARKC). B1AW displayed anti-bacterial activity against Gram-positive bacteria Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA), and Enterococcus faecalis (E. faecalis). B1AW-K was designed to broaden the antimicrobial spectrum of B1AW. The introduction of a lysine residue generated an AMP with enhanced broad-spectrum antibacterial activity. It also displayed the ability to inhibit the growth of human prostatic cancer PC-3, non-small lung cancer H838, and glioblastoma cancer U251MG cell lines. In molecular dynamic (MD) simulations, B1AW-K had a faster approach and adsorption to the anionic membrane than B1AW. Therefore, B1AW-K was considered a drug prototype with a dual effect, which deserves further clinical investigation and validation.

Identification of a new myotropic decapeptide from the skin secretion of the red-eyed leaf frog, Agalychnis callidryas

Bradykinin-related peptides (BRPs) family is one of the most significant myotropic peptide families derived from frog skin secretions. Here, a novel BRP callitide was isolated and identified from the red-eyed leaf frog, Agalychnis callidryas, with atypical primary structure FRPAILVRPK-NH₂. The mature peptide was cleaved N-terminally at a classic propeptide convertase cleavage site (-KR-) and at the C-terminus an unusual -GKGKGK sequence was removed using the first G residue as an amide donor for the C-terminally-located K residue. Thereafter, the synthetic replicates of callitide were assessed the myotropic activity and showed a significant contraction of balder, with the 0.63 nM EC₅₀ value, more potent than most discovered myotropic peptides. The binding mode was further speculated by molecular docking and stimulation. The result indicated that the C-terminal of callitide might selectively bind to bradykinin receptor B2 (BKRB2). Further investigation of the callitide needs to be done in the future to be exploited as potential future drug leads.

Pharmacological Effects of a Novel Bradykinin-Related Peptide (RR-18) from the Skin Secretion of the Hejiang Frog (Ordorrana hejiangensis) on Smooth Muscle

Bradykinin (BK) and bradykinin-related peptides (BRPs), which were identified from a diversity of amphibian skin secretions, exerted contractile and relaxing effects on non-vascular and vascular smooth muscle, respectively. Here, we report a novel bradykinin-related peptide with a molecular mass of 1890.2 Da, RVAGPDKPARISGLSPLR, which was isolated and identified from Ordorrana hejiangensis skin secretions, followed by a C-terminal extension sequence VAPQIV. The biosynthetic precursor-encoding cDNA was cloned by the “shotgun” cloning method, and the novel RR-18 was identified and structurally confirmed by high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). Subsequently, the myotropic activity of the synthetic replicate of RR-18 was investigated on the rat bladder, uterus, tail artery and ileum smooth muscle. The peptide was named RR-18 in accordance (R = N-terminal arginine, R = C-terminal arginine, 18 = number of residues). In this study, the synthetic replicates of RR-18 showed no agonist/antagonism of BK-induced rat bladder and uterus smooth muscle contraction. However, it displayed an antagonism of bradykinin-induced rat ileum contraction and arterial smooth muscle relaxation. The EC₅₀ values of BK for ileum and artery, were 214.7 nM and 18.3 nM, respectively. When the tissue was pretreated with the novel peptide, RR-18, at the maximally effective concentration of bradykinin (1 × 10⁻⁶ M), bradykinin-induced contraction of the ileum and relaxation of the arterial smooth muscle was reduced by 50–60% and 30–40%, respectively. In conclusion, RR-18 represents novel bradykinin antagonising peptide from amphibian skin secretions. It may provide new insight into possible treatment options for chronic pain and chronic inflammation.

Molecular characterization, purification, and antioxidant activity of recombinant superoxide dismutase from the Pacific abalone Haliotis discus hannai Ino

Superoxide dismutase (SOD) is an acidic metalloenzyme that scavenges free radicals produced by endogenous and exogenous substances. In the present study, the tissue distribution of the superoxide dismutase HdhCu/Zn-SOD was investigated in Haliotis discus hannai Ino. The expression profile after lipopolysaccharide (LPS) challenge was determined using quantitative real-time polymerase chain reaction (qPCR). To study the antioxidant activity of a recombinant HdhCu/Zn-SOD protein, the HdhCu/Zn-SOD gene was cloned into the pPIC9K vector and transformed into the Pichia pastoris GS115 strain by electroporation. After induction by methanol, the recombinant product was purified using immobilized metal affinity chromatography and confirmed using mass spectrometry. The optimal expression conditions were determined to be incubation with 0.5% methanol at pH 6.0, resulting in a stable expressed product with the molecular weight of approximately 17 kDa and 21 kDa. The enzymatic activity of HdhCu/Zn-SOD consistently increased with increasing Cu²⁺ concentrations and showed good thermal stability. Recombinant HdhCu/Zn-SOD showed a strong ability to scavenge superoxide anions and hydroxyl radicals and protected L929 cells against the toxicity caused by H₂O₂ through its in vitro antioxidant activity. The heterologous expression of HdhCu/Zn-SOD in P. pastoris and the antioxidant activity of this enzyme are reported for the first time.

Introduction to the Toxins Special Issue on Identification and Functional Characterization of Novel Venom Components

Throughout most of the 20th century, the toxinological literature consisted largely of pharmacological and functional characterizations of crude venoms and venom constituents, often constituents that could not be identified unambiguously [...].