Calmodulin mediated activation of acetyl-CoA carboxylase during aflatoxin production by Aspergillus parasiticus.
The relevance of Ca2+-calmodulin-mediated processes in channelling acetate for aflatoxin formation was investigated by studying the influence of trifluoperazine (an anticalmodulin agent) on [14C]-acetate incorporation and activity of acetyl-CoA carboxylase in Aspergillus parasiticus NRRL 2999. Culturing the organism in presence of 0.14 mmol l-1 trifluoperazine resulted in 55% decrease of [14C]-acetate incorporation into aflatoxin B1, along with an 80% decrease in acetyl-CoA carboxylase activity at periods corresponding to maximal aflatoxin production. Concomitant decrement (35%) in the activity of glucose-6-phosphate dehydrogenase indicated decreased availability of reduction potential (NADPH) required for aflatoxin biosynthesis. The ability of calmodulin to activate and trifluoperazine to inhibit acetyl-CoA carboxylase activity in a dose-dependent manner was also noted under in vitro conditions. The combined results suggest calmodulin-mediated activation of acetyl-CoA carboxylase as an important event for aflatoxin production.
Rao
J P
JP
Department of Biochemistry, Osmania University, Hyderabad, AP, India.
Subramanyam
C
C
D000085:Acetates / Q000378:metabolism; D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000348:Aflatoxins / Q000096:biosynthesis*; D001230:Aspergillus / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000378:metabolism; D004789:Enzyme Activation; D014268:Trifluoperazine / Q000378:metabolism
D000085:Acetates; D000348:Aflatoxins; D002147:Calmodulin; D002250:Carbon Radioisotopes; D014268:Trifluoperazine; D000103:Acetyl-CoA Carboxylase