Fatty acids from the cyanobacterium Microcystis aeruginosa with potent inhibitory effects on fish gill Na+/K+-ATPase activity.
Fatty acids from two strains of the cyanobacterium Microcystis aeruginosa, PCC 7820 (a strain that produces the hepatotoxin microcystin-LR, MC-LR) and CYA 43 (a strain that produces only small quantities of MC-LR), were extracted, partially characterised and tested for their inhibitory effect on the K+-dependent p-nitrophenol phosphatase (pNPPase) activity of tilapia (Oreochromis mossambicus) gill basolateral membrane. Thin-layer chromatography of the lipids from dichloromethane:methanol extracts of M. aeruginosa PCC 7820 and CYA 43, using diethylether:isopropanol:formic acid (100:4.5:2.5) as solvent, yielded five inhibitory products from M. aeruginosa 7820 and six from M. aeruginosa CYA 43. None of these products could be related to MC-LR. The inhibitory behaviour of the products mimics that of a slow, tight-binding inhibitor. The inhibitory activity is removed by incubation of extracts with fatty-acid-free bovine serum albumin (FAF-BSA). However, FAF-BSA only partially reversed the inhibition of K+-dependent pNPPase on fish gills pre-exposed to the extracted products. We conclude that M. aeruginosa strains PCC 7820 and CYA 43 produce fatty acids with potent inhibitory effects on K+-dependent pNPPase. The release of these products following lysis of cyanobacterial blooms may help to explain fish kills through a disturbance of gill functioning.
Bury
N R
NR
Department of Animal Physiology, University of Nijmegen, The Netherlands.
Codd
G A
GA
Wendelaaar Bonga
S E
SE
Flik
G
G
D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005227:Fatty Acids / Q000302:isolation & purification / Q000494:pharmacology*; D005880:Gills / Q000201:enzymology*; D046931:Microcystis / Q000737:chemistry*; D011188:Potassium / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D017210:Tilapia
D004791:Enzyme Inhibitors; D005227:Fatty Acids; D012710:Serum Albumin, Bovine; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium