Purification and Characterization of a Microsomal Bile Acid β-Glucosidase from Human Liver

摘要: Abstract A human liver microsomal β-glucosidase has been purified to apparent homogeneity in sodium dodecyl sulfate-polyacrylamide gel electrophoresis where a single protein band of Mr 100,000 was obtained under reducing conditions. The enzyme enriched about 73,000-fold over starting membranes by polyethylene glycol fractionation, anion exchange chromatographies on DEAE-Trisacryl, and Mono Q followed affinity chromatography N-(9-carboxynonyl)-1-deoxynojirimycin-AH-Sepharose 4B. had pH optimum between 5.0 6.4, activated divalent metal ions, required phospholipids for exhibition activity. catalyzed the hydrolysis 3β-D-glucosido-lithocholic 3β-D-glucosido-chenodeoxycholic acids with high (Km, 1.7 6.2 μM, respectively) β-D-glucoside 210 μM) β-D-galactoside 4-methylumbelliferone. ratio relative reaction rates these substrates 6:3:11:1. No activity detectable toward 6β-D-glucosido-hyodeoxycholic acid, glucocerebroside, following glycosides 4-methylumbelliferone: α-D-glucoside, α-L-arabinoside, β-D-fucoside or β-D-xyloside. Immunoinhibition immunoprecipitation studies using antibodies prepared against lysosomal glucocerebrosidase showed no cross-reactivity suggesting that two enzymes are antigenically unrelated.