Conjugation of benzo[a]pyrene metabolites by freshwater green alga Selenastrum capricornutum.
Benzo[a]pyrene (BaP) undergoes metabolic transformation in mammals via oxidative, hydrolytic, and conjugative processes; however, little is known concerning BaP conjugation in freshwater algae. It has been shown in this laboratory that BaP is metabolized by Selenastrum capricornutum via a dioxygenase pathway. This study describes the conjugation of BaP metabolites by a green alga, Selenastrum capricornutum. Cultures were exposed to 1160 micrograms/l [14C]BaP for 4 days at 23 degrees C under gold fluorescent lights on a diurnal cycle of 16 h light, 8 h dark. Of the total metabolites in the algal culture, 89% were present in media. BaP and non-conjugated metabolites were separated from conjugated metabolites by chromatography on neutral alumina columns using solvents of increasing polarity. Seventy-one percent of the BaP metabolites were conjugates of which 12.2%, 12.0% and 12.4% were sulfate ester and alpha- and beta-glucose conjugates, respectively. Conjugates that coeluted with sulfate esters were hydrolyzed with arylsulfatase, alpha- or beta-glucosidase; high performance liquid chromatography (HPLC) analysis indicated that the major product of each enzymatic hydrolysis was the 4,5-dihydrodiol (87.2, 69 and 53%, respectively). Eighty-six percent of the conjugates were acid labile following incubation for 2 h in 4 N HCl at 37 degrees C. To our knowledge this is the first demonstration of the metabolism of a polynuclear aromatic hydrocarbon by a freshwater green alga through a dioxygenase pathway and subsequent conjugation and excretion.
Warshawsky
D
D
Department of Environmental Health, University of Cincinnati Medical Center, OH 45267-0056.
Keenan
T H
TH
Reilman
R
R
Cody
T E
TE
Radike
M J
MJ
D000135:Acid Phosphatase; D001192:Arylsulfatases; D001564:Benzo(a)pyrene / Q000302:isolation & purification / Q000378:metabolism*; D001711:Biotransformation; D002250:Carbon Radioisotopes; D000460:Chlorophyta / Q000254:growth & development / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D000520:alpha-Glucosidases; D001617:beta-Glucosidase
D002250:Carbon Radioisotopes; D001564:Benzo(a)pyrene; D000135:Acid Phosphatase; D001192:Arylsulfatases; D000520:alpha-Glucosidases; D001617:beta-Glucosidase