Effects of Some Alkali and Alkaline Earth Metal Ions on the Initial Reaction Rates of Congregibacter litoralis KT71 β-lactamase Hydrolysis of 4-Nitrophenyl Myristate

Abstract

The effects of some alkali metal ions (Na+ and K+) and alkaline earth metal ions (Mg 2+ and Ba2+) on the initial reaction rates of Congregibacter litoralis KT71 β-lactamase hydrolysis of 4-nitrophenyl myristate was investigated by varying the concentrations of the metal ions in the assay mixture which comprised of 100 µl of standard enzyme solution, 200 µl of varying concentration of metal ions, 500 µl of 50 mM sodium phosphate buffer pH 7.5 and 200 µl of 4-nitrophenyl myristate (substrate) which was added last to the assay mixture after an incubation time of 10 minutes at 44 oC. The enzyme activity was measured spectrophotometrically using a UV-780 recording spectrophotometer at a wavelength of 405 nm. The hydrolysis of 4-nitrophenyl myristate to yield 4-nitrophenol was monitored by reading the absorbance at 25 minutes. Results showed that the alkaline earth metal ions (Ba2+ and Mg2+) had higher enzyme activation effect than the alkali metal ions (K+ and Na+) Also, all metal ions except Mg2+ showed enzyme stimulatory effect at low concentrations (<2 mM) but inhibitory at higher ion concentrations (2 mM - 3 mM). Mg 2+ caused a proportionate decrease in enzyme activity from its peak (when metal ion concentration was lowest). Results from this research is of great significance to the industrialist especially where the search for novel lipases with unique characteristics suitable for the industries are inevitable.