Estimation of kinetic parameter for the biotransformation of three-ring azaarenes by the phenanthrene-degrading strain Sphingomonas sp. LH128.
We examined the biotransformation of several azaarenes to get information on their rate of removal from contaminated soil by cometabolic degradation. Acridine, 9-methyl-acridine, phenanthridine, benzo[f]quinoline, and benzo[h]quinoline were found to be cometabolized by phenanthrene-degrading Sphingomonas sp. strain LH128. The transformation of acridine and benzo[h]quinoline was shown to be inhibited at relatively high concentrations (24.9 mg/L and 58.2 mg/L, respectively). Maximum biotransformation rates (Vmaxs), Michaelis-Menten half saturation constants (Kms), and biotransformation constants (k1s) were estimated for acridine, phenanthridine, and benzo[f]quinoline and ranged from 14.0 to 26.1 mg/g total protein/h for Vmax, 0.57 to 2.9 mg/L for Km, and 4.9 to 30.8 L/g total protein/h for k1. For 9-methyl-acridine only, a k1 of 0.6 L/g total protein/h was estimated and for benzo[h]quinoline, the highest biotransformation rate measured was 6.8 +/- 0.4 mg/g total protein/h. To our knowledge, this is the first effort to determine both Vmax and Km kinetic parameters describing the biotransformation of phenanthrene- and anthracene-analogue azaarenes. The results show that the rate of removal of azaarenes from contaminated soil will probably be rather high, although accumulation of metabolites can be expected.
van Herwijnen
René
R
Department of Environmental and Toxicological Chemistry (IBED/MTC), University of Amsterdam, Nieuwe Achtergracht 166, 1018WV Amsterdam, The Netherlands.
de Graaf
Chris
C
Govers
Harrie A J
HA
Parsons
John R
JR
D001372:Aza Compounds / Q000378:metabolism*; D001711:Biotransformation; D004787:Environmental Pollution / Q000517:prevention & control*; D006575:Heterocyclic Compounds, 3-Ring / Q000378:metabolism*; D007700:Kinetics; D012044:Regression Analysis; D012988:Soil Microbiology; D020578:Sphingomonas / Q000378:metabolism*
D001372:Aza Compounds; D006575:Heterocyclic Compounds, 3-Ring