Fractionation, biochemical characterization and lysosomal phospholipases of human liver

Abstract

Human liver was homogenised and fractionated by differential centrifugation, and the s&cellular fractions were characterised biochemically. Absolute values and distribution patterns of protein and marker enzyme activities obtained from human liver have also heen compared with those from rat liver. In addition, acid phospholipase activities have been studied in human liver. On the basis of product formation from stereospecifically radiolaheled phosphatidylethanolamine substrates, lysosomal phospholipases A, and A, with optimal activities at pH 4.7 have heen identified in human liver. Acid phospholipase C and lysophospholipase activities, however, were not found in human liver. Cationic amphiphilic drugs inhibited the activities of the acid phospholipases A in human and rat liver lysosomes to about the same extent.

Subcellular distribution of glycosylphosphatidylinositol-specific phospholipase D in rat liver

“…The purities of the preparations were analysed biochemically by measuring marker enzyme activities as described previously [22][23][24]. The distribution of the constituents and the relative specific activities (RSAs) of the enzymes in the fractions were calculated as described by de Duve et al [18].…”

Cationic factors affecting phospholipase activities from human lung

“…(Lanni & Becker, 1983;Chang et al, 1985;Alonso et al, 1986), all have pH optima between pH 7.5 and pH 9. Lysosomal PLA2 from human liver (Loffler & Kunze, 1987) or from rabbit alveolar macrophages (Franson et al, 1973) shows an acid optimum at about pH 4. Although we were able to show a relative concentration of lysosomal marker enzymes in the P1 fraction, our results on PLA2 activity in P1 showed no sign of a pH optimum markedly different from that for the PLA2 activity in the microsomal fraction (P2).…”