Kinetic studies of alkaline phosphatase extracted from rabbit (Lepus townsendii) 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.