Purification and partial characterization of three dipeptidases from rat liver

ABSTRACT

Three dipeptidases namely; Leu-Leu dipeptidase [LLD], Leu-gly dipeptidase [LGD] and Ala-gly dipeptidase [AGD] from rat liver were purified using L. Leu-Leu, L, Leu-gly and L.Ala-gly as substrates. The adopted purification techniques included treatment with n-butanol, acetone precipitation and drying, ammonium sulphate fractionation, DEAE-cellulose chromatography, second acetone precipitation and sephadex G-200 gel filtration. Performance of kinetic studies proved that the enzyme preparation acting on L. Ala-gly as substrate exhibited a kinetic behavior different from those acting on L. Leu-Leu and L-Leu-gly dipeptides. The data proved that LLD and LGD displayed similar behaviour with respect to activation with Mn[2+], the incidence of positive cooperativity and pH optima. However, discrepances in behaviour were indicated with respect to Km [10.0 x 10[-3] M and 8.7 x 10[-3] M for LLD and LGD respectively], pH end thermal stability. Addition of activators and inhibitors proved that the separated enzymes were metalloenzymes