ABSTRACT
Objective To explore the effects of humulon on kinetic parameters of N-acetyltransferase-1(NAT1) of human gastric cancer SGC-7901.Methods Employing HPLC,using para-aminobenzoic acid(PABA) as substrate,in intact SGC-7901 cells and their cytoplasm,taking the speed of PABA being acetylated to Ac-PABA by NAT1 as the rate of NAT1,using double reciprocal plot,taking the reciprocal of concentration of PABA and reaction rate of NAT1 as coordinates,regression equation was obtainied and the Michaelis constant(Km) and maximum reaction velocity(Vmax) were calculated.Results Study on enzyme kinetics demonstrated,as for intact SGC-7901 cells,Km and Vmax of control group were(3.910?0.087) ?mol/L and(0.306 0?0.006 7) pmol/L(1?106 cells),respectively,Km and Vmax of the humulon group were(3.830?0.123) ?mol/L and(0.275 0?0.005 8) pmol(1?106 cells),respectively.As for the cytoplasm of SGC-7901 cells,Km and Vmax of control group were(760.2?210.2) ?mol/L and(0.191 0?0.043 7) pmol/(mg?min),Km and Vmax of the humulon group were(449.0?72.9) ?mol/L and(0.094 0?0.010 4) pmol/(mg?min).Statistically,as for intact SGC-7901 cells or their cytoplasm,there was no difference of the Km between control group and humulon group,but there was remarkable difference of Vmax between control group and humulon group,P