nitrophenols has been researched along with triphenyl-phosphate* in 2 studies
2 other study(ies) available for nitrophenols and triphenyl-phosphate
| Article | Year |
|---|---|
The Michaelis constants of a nonchromogenic substrate may be determined using a chromogenic substrate.
A general method is presented for the determination of the KM and Vmax for a nonchromogenic substrate in an experimental system where a chromogenic and a nonchromogenic substrate compete for the active site of a single enzyme. Entire progress curves of absorbance versus time for the transformation of the chromogenic substrate must be obtained in the absence and presence of the nonchromgenic substrate. Two quantities may then be extracted from the entire kinetic curves: the value of a delta Area, the area bounded by the kinetic traces of absorbance versus time in the presence and absence of the nonchromogenic substrate; and the value of delta t(5%), the time required to transform 5% of the chromogenic substrate in the presence of the nonchromogenic substrate minus the corresponding time required in its absence. The values of KM and Vmax for the nonchromogenic substrate may be obtained from the dependencies of delta Area and delta t(5%) upon the concentration of the nonchromogenic substrate. The ability of this procedure to yield the correct values of KM and Vmax was demonstrated using beta-lactamase, beta-galactosidase, alkaline phosphatase, and 19 chromogenic/nonchromogenic substrate pairs. This method is equally valid in the absence or presence of competitive product inhibition and should be applicable to any enzyme-catalyzed, strongly exergonic reaction. Topics: Alkaline Phosphatase; beta-Galactosidase; beta-Lactamases; Binding Sites; Binding, Competitive; Cephalosporins; Chromogenic Compounds; Galactosidases; Kinetics; Nitrophenols; Organophosphates; Organophosphorus Compounds; Penicillin G; Spectrophotometry | 1989 |
L-Phenylalanine inhibition of human alkaline phosphatases with p-nitrophenyl phosphate as substrate.
With p-nitrophenyl phosphate as the substrate, there reportedly is no organ-specific inhibition of alkaline phosphatase (EC 3.1.3.1) activity by L-phenylalanine. However, we found that at pH 10.0, with p-nitrophenyl phosphate as the substrate, L-phenylalanine obviously inhibits the alkaline phosphatase isoenzyme from human placenta, whereas there is little if any inhibition of the isoenzyme from human intestine. Because of the differing effects of substrates (p-nitrophenyl phosphate and phenyl phosphate) and their enzymic products (p-nitrophenol and phenol) for L-phenylalanine action on the placental alkaline phosphatase isoenzyme, we suggest that the isoenzyme--inhibitor--substrate complex and the effect of released phosphate on L-phenylalanine inhibition of the isoenzyme activity differ from each other. Topics: Adult; Alkaline Phosphatase; Enzyme Activation; Female; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Intestinal Mucosa; Nitrophenols; Organophosphates; Organophosphorus Compounds; Phenylalanine; Placenta | 1982 |