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Biological activities of prymnesin-2 isolated from a red tide alga Prymnesium parvum
T Igarashi1, S Aritake, T Yasumoto
1Department of Applied Biochemistry, Faculty of Agriculture, Tohoku University, Sendai, Japan.
Abstract:
Previously we isolated prymnesin-1 (PRM1) and prymnesin-2 (PRM2) as the major hemolytic and ichthyotoxic agents in the red tide organism Prymnesium parvum and disclosed the structure of PRM2 as a novel glycoside with unusual multiple functionality. PRM2 caused 50% hemolysis of a 1% suspension of dog red blood cells at 0.5 nM. The potency exceeded that of plant saponin by 50000 times. The lethality of PRM2 on freshwater fish Tanichthys albonubes was comparable to that of brevetoxin and also the ichthyotoxicity was markedly enhanced by Ca2+ and by a slight elevation of pH: LC50 in a Ca2+ free medium (pH 7.0) was 300 nM and in the presence of 2 mM Ca2+ (pH 8.0) was 3 nM. The hemolytic activity of PRM2 was not affected by Ca2+ but was markedly affected by blood cell origin. Also, the observation of competitive inhibition by the PRM2 analogues allowed us to assume the presence of a specific binding site on the blood cell surface.
Insights
Prymnesin-2 (PRM2), a potent toxin from Prymnesium parvum, causes significant hemolysis and fish toxicity. Its activity is influenced by calcium ions and pH, suggesting a specific cell surface binding site.
Area of Science:
- Marine biology
- Toxicology
- Biochemistry
Background:
- Prymnesium parvum is a harmful algal bloom species responsible for fish kills.
- Prymnesin-1 (PRM1) and prymnesin-2 (PRM2) were previously identified as major toxins.
- The structure of PRM2 was revealed as a novel glycoside with unique functional groups.
Purpose of the Study:
- To characterize the hemolytic and ichthyotoxic properties of prymnesin-2 (PRM2).
- To investigate the influence of environmental factors like calcium ions (Ca2+) and pH on PRM2 toxicity.
- To explore the mechanism of PRM2 action, including potential binding sites on cell surfaces.
Main Methods:
- Isolation and purification of prymnesin-1 (PRM1) and prymnesin-2 (PRM2).
- Hemolysis assays using dog red blood cells.
- Lethality assays on freshwater fish (Tanichthys albonubes).
- Toxicity assessments under varying Ca2+ concentrations and pH levels.
- Competitive inhibition assays with PRM2 analogues.
Main Results:
- PRM2 exhibited extremely high hemolytic potency (0.5 nM for 50% hemolysis), vastly exceeding plant saponins.
- PRM2 demonstrated significant ichthyotoxicity, comparable to brevetoxin.
- PRM2's ichthyotoxicity was dramatically enhanced by Ca2+ and slightly elevated pH (e.g., LC50 decreased from 300 nM to 3 nM).
- Hemolytic activity was independent of Ca2+ but varied with blood cell origin.
- Competitive inhibition suggested a specific binding site for PRM2 on blood cell surfaces.
Conclusions:
- PRM2 is a highly potent hemolytic and ichthyotoxic agent produced by Prymnesium parvum.
- Calcium ions and pH significantly modulate PRM2's toxicity towards aquatic organisms.
- Evidence suggests the existence of specific binding sites for PRM2 on cell surfaces, mediating its toxic effects.