Bile salt-dependent lipase biosynthesis in rat pancreatic AR 4-2 J cells. Essential requirement of N-linked oligosaccharide for secretion and expression of a fully active enzyme.

摘要: This study used the rat pancreatic AR 4-2 J cell line as a model system to investigate role of glycosylation in bile salt-dependent lipase (BSDL) secretion and esterolytic activity. Results indicated that cells synthesized BSDL, activity which was greater part toward 4-nitrophenylcaproate. The protein thus expressed glycosylated had molecular mass approximately 74 kDa. Exposure these tunicamycin significantly decreased [3H]mannose incorporation, while [35S]methionine incorporation trichloroacetic acid-precipitable material not modified. Tunicamycin treatment lead lower form (approximately 70 kDa) BSDL did incorporate [3H]mannose. nonglycosylated low M(r) enzyme secreted shown by decreasing cell-free medium paralleled time-dependent enzyme. no effect on synthesis. Nevertheless, apparently degraded any compartment accumulation within upon brefeldin A treatment. characterized Km 68 +/- 30 microM kcat 106 19 min-1. sequestrated due presents significant increase over 10 times 757 303 microM. affected factor 4-445 22 These data correlated with an 2.5-fold decrease following inhibition N-glycosylation protein. less stable temperature than native form. Processing inhibitors (castanospermine, 1-deoxymannojirimycin, swainsonine) either or its secretion. suggested first transfer oligosaccharide precursor nascent is essential for folding fully active BSDL. Second glycan structure required