sodium-dodecyl-sulfate and 4-4--dipyridyl-disulfide

Recombinant human gastric lipase (rHGL) and three of its cysteine mutants (cysteine 227, 236, and 244 substitued for threonine or serine) were expressed in the baculovirus/insect cell system and purified to homogeneity by performing a two-step procedure. Substituting Ser for Cys 227 and Cys 236 resulted in mutant lipases with a significantly lower level of activity (30% and 22%, respectively) on a short chain triglyceride (tribuyrin) substrate, while the mutation at position 244 only slightly reduced the activity. Using 4, 4'-dithiopyridine (4-PDS) as a sulfhydryl reagent on the above mutants, it was possible to clearly identify the single sulfhydryl residue at position 244 and consequently, the disulfide bridge at position 227-236. No potential disulfide bridges were formed during the protein folding between cysteines 227-244 or between cysteines 236-244, as thought to occur in the case of rabbit gastric lipase (RGL). The present results are consistent with the recently determined 3D-structure of rHGL.

Topics: Amino Acid Substitution; Animals; Baculoviridae; Catalysis; Cell Line; Cysteine; Disulfides; Gastric Mucosa; Humans; Insecta; Kinetics; Lipase; Protein Folding; Pyridines; Recombinant Proteins; Sodium Dodecyl Sulfate; Titrimetry; Triglycerides