Rapid determination of enzyme kinetics from fluorescence: overcoming the inner filter effect.
Fluorescence change is convenient for monitoring enzyme kinetics. Unfortunately, it loses linearity as the absorbance of the fluorescent substrate increases with concentration. When the sum of absorbance at excitation and emission wavelengths exceeds 0.08, this inner filtering effect (IFE) alters apparent initial velocities, K(m), and k(cat). The IFE distortion of apparent initial velocities can be corrected without doing fluorophore dilution assays. Using the substrate's extinction coefficients at excitation and emission wavelengths, the inner filter effect can be modeled during curve fitting for more accurate Michaelis-Menten parameters. A faster and simpler approach is to derive k(cat) and K(m) from progress curves. Strategies to obtain reliable and reproducible estimates of k(cat) and K(m) from only two or three progress curves are illustrated using matrix metalloproteinase 12 and alkaline phosphatase. Accurate estimates of concentration of enzyme-active sites and specificity constant k(cat)/K(m) (from one progress curve with [S]<<K(m)) confer accuracy, freedom of choices of [S], and robustness to k(cat) and K(m) globally fitted to a few progress curves. The economies of the progress curve approach make accurate k(cat) and K(m) more accessible from fluorescence measurements.
Palmier
Mark O
MO
Department of Biochemistry, University of Missouri-Columbia, 117 Schweitzer Hall, Columbia, MO 65211, USA.
Van Doren
Steven R
SR
D000465:Algorithms; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002021:Buffers; D002417:Cattle; D002852:Chromatography, Ion Exchange; D004151:Dipeptides / Q000494:pharmacology; D004798:Enzymes / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005374:Filtration / Q000295:instrumentation / Q000592:standards; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D006863:Hydrogen-Ion Concentration; D002479:Inclusion Bodies / Q000737:chemistry; D007413:Intestinal Mucosa / Q000201:enzymology; D007700:Kinetics; D053508:Matrix Metalloproteinase 12 / Q000032:analysis / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D011485:Protein Binding; D012995:Solubility; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013379:Substrate Specificity; D014508:Urea / Q000494:pharmacology
D002021:Buffers; D004151:Dipeptides; D004798:Enzymes; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D014508:Urea; D000469:Alkaline Phosphatase; D053508:Matrix Metalloproteinase 12
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