An assessment of the role of intracellular reductive capacity in the biological clearance of triarylmethane dyes.
The second-order rate constants (at pH 7, 25 degrees C) for the reduction of three cationic triarylmethane dyes [pararosaniline (PR+), malachite green (MG+), methyl green (MeG+)] by NADH were 1.4 x 10(-2) to 6.7 x 10(-2)mM(-1)min(-1). Based on these values the intracellular nonenzymatic reduction of TAM+ to TAM-H by endogenous NADH was estimated to proceed with an average half-life of 30 min. Rapid and significant adduct formation was observed with the thiol, 3-mercaptopropionic acid (MPA), suggesting that the primary intracellular form of the dyes must be a thiol adduct and that the conversion to adduct form takes place within ms-s. These time frames, when compared to the min-h time frame for microbial clearance of triarylmethanes from culture media, suggest that transport must be the rate-limiting step in non-adsorptive (chemical) clearance of the dyes and that the presence of enzymes to complement the nonenzymatic reductive and adduct-forming activities cited serves a kinetically limited purpose. It appears that a superior catalytic scavenger will be one with a superior transport capacity.
Tacal
Ozden
O
Department of Biochemistry, School of Pharmacy, Hacettepe University, 06100 Ankara, Turkey. tacal@hacettepe.edu.tr
Ozer
Inci
I
D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000737:chemistry*; D015394:Molecular Structure; D009243:NAD / Q000737:chemistry; D010084:Oxidation-Reduction; D012394:Rosaniline Dyes / Q000737:chemistry
D004396:Coloring Agents; D012394:Rosaniline Dyes; D009243:NAD; C005095:malachite green; D008697:Methane