Kinetic studies of alkaline phosphatase extracted from rabbit (<i>Lepus townsendii</i>) liver

Abstract

Studies were carried out to ascertain some kinetic properties of alkaline phosphatase (ALP) extracted from Lepus townsendii liver. Incubation of ALP extract with 4-nitrophenylphosphate (4-NPP) formed the basis for determination of enzyme activity. Spectrophotometric method was used to assay the enzyme activity, and the kinetic constants-maximum enzyme velocity (V_max) and Michealis-Menten constant (K_m) were evaluated. The K_m and V_max values were 0.5 x 10^-3 M and 20 x 10^-6 M/min, respectively. Inhibition studies showed that ALP activity was competitively inhibited by 0.67 mM sodium hydrogen orthophosphate (NaH₂PO₄) and the inhibition constant (K_i) was 0.9 x 10^-3 M. The optimum pH value for ALP activity was about 9.2, and optimum temperature registered was 45°C. ALP activity exhibited linear Arrhenius relationship at temperature greater than 44.95°C with corresponding catalytic energy of activation (E_a) = 15.23 KJ mole^-1. The present study gave insights into characteristic catalytic properties of ALP extracted from L. townsendii liver.

Key words: Alkaline phosphatase, Lepus townsendii,  4-nitrophenylphosphate (4-NPP), Arrhenius relationship, Michealis-Menten constant.