Lack of proteolytic processing of α-L-fucosidase in human skin fibroblasts

✍ Scribed by Debra M. Leibold; Cynthia B. Robinson; Thomas F. Scanlin; Mary Catherine Glick

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 909 KB
• Volume: 137
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041370304

✦ Synopsis

Acid hydrolases are synthesized as precursors that undergo several posttranslational modifications including proteolytic processing to a smaller mature enzyme. The amount of proteolytic processing varies for different acid hydrolases, and many details of the intracellular pathways are not known. The processing of a-L-fucosidase was distinguished from that of other acid hydrolases reported when studied in systematic pulse-chase labeling experiments. Only one form of a-L-fucosidase, M, 56,000-57,000, was demonstrated intra-and extracellularly. Under the same conditions, i+acetyl-P-o-glucosaminidase was shown to be processed with several forms, as previously reported by Hasilik and Neufeld (1 980a). To obtain these results, human skin fibroblasts were labeled metabolically with ~-[ ~H l l e u c i n e for periods of 20 min to 8 hr with varying periods of chase from 1 to 96 hr with nonradioactive L-leucine. a-i-Fucosidase was immunoprecipitated by a polyclonal antibody from material extracted from cells and ammonium sulfate precipitated medium and was examined by polyacrylamide gel electrophoresis under denaturing conditions. N-Acetyl-p-D-glucosaminidase was examined with similar procedures and served as a control for the methods. Tunicamycin treatment of the cells was used to show that glycosylation did not obscure proteolytic proces5Ing because, again, only one form of the intra-and extracellular enzyme was observed, although of smaller size, M, 52,000-53,000. In addition, separation of the cells into prelysosomal and lysosomal fractions showed only one form of the enzyme. It i s concluded that a-L-fucosidase does not undergo proteolytic processing in human skin fibroblasts in the usual manner described for other acid hydrolases.