. Author manuscript; available in PMC: 2010 Apr 23.

Published in final edited form as: Toxicol Appl Pharmacol. 2008 Dec 9;235(2):143–152. doi: 10.1016/j.taap.2008.11.017

Table 2.

Enzymatic kinetic characterization of fenthion metabolites in microsomal fractions isolated from liver from freshwater- and hypersaline-acclimated rainbow trout (Oncorhynchus mykiss) and incubated with fenthion

Metabolite	Freshwater			Hypersaline
Metabolite	K_m (μM)	V_max (pmol/min/mg protein)	V_max/K_m	K_m (μM)	V_max (pmol/min/mg protein)	V_max/K_m
MMTP (NADPH-independent)	292.0±66.6	53.7±4.8	0.18	652.0±221.1	59.8±10.5	0.09
MMTP (NADPH-dependent)	86.6±37.8	199.2±24.4	2.06	136.4±23.1	35.1±1.9	0.25
Fenoxon	115.7±21.1	82.8±4.6	0.72	187.2±25.2	130.0±6.1	0.69
S-fenthion sulfoxide	264.4±38.2	173.4±9.6	0.66	103.8±9.4	355.7±9.4	3.42
R-fenthion sulfoxide	293.3±48.6	78.6±5.2	0.27	142.0±26.3	201.1±11.9	1.41
S-fenoxon sulfoxide	ND	bdl	ND	114.5±31.5	18.4±1.1	0.16
R-fenoxon sulfoxide	ND	bdl	ND	132.6±33.3	7.7±0.6	0.06

Data are presented as mean±SD (n=8 individuals with 2 replicates for each one).

MMTP: 3-methyl-4-(methylthio)-phenol.

ND: not determined.

bdl: below detection limit (<0.3 pmol/min/mg protein).