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Proteolytic processing of human lysosomal arylsulfatase A
T Fujii1, T Kobayashi, K Honke
1Biochemistry Laboratory, Hokkaido University School of Medicine, Sapporo, Japan.
Biochimica Et Biophysica Acta
|July 13, 1992
Summary
Human arylsulfatase A has three subunits: 58 kDa, 50 kDa, and 7 kDa. The 50 kDa and 7 kDa subunits are generated from the 58 kDa subunit through limited proteolysis, indicating tissue-independent processing.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Arylsulfatase A is an enzyme with known 58 kDa and 50 kDa components.
- An additional 7 kDa component in human placental arylsulfatase A was previously unreported.
- The structural relationship between these subunits was not fully understood.
Purpose of the Study:
- To elucidate the subunit structure of human arylsulfatase A.
- To define the relationship between the 58 kDa, 50 kDa, and 7 kDa components.
- To investigate potential tissue-specific variations in arylsulfatase A processing.
Main Methods:
- N-terminal sequencing of the 58 kDa, 50 kDa, and 7 kDa components.
- Peptide mapping using trypsin and Achromobacter proteinase I.
- Sequence analysis of peptide fragments.
- Unreduced SDS-PAGE to detect disulfide bonds.
Main Results:
- The 50 kDa component is identical to the 58 kDa component except for a C-terminal truncation (lacking Val-445 to C-terminus).
- The 7 kDa component represents a further C-terminal fragment, starting near Val-445.
- The 58 kDa and 7 kDa components are linked by disulfide bonds.
- Arylsulfatase A from human liver exhibited the same subunit composition and processing as the placental enzyme.
Conclusions:
- Human arylsulfatase A undergoes limited proteolysis near the C-terminus of the 58 kDa subunit to generate the 50 kDa and 7 kDa components.
- Disulfide bonds link the 58 kDa and 7 kDa subunits.
- This proteolytic processing pathway appears conserved across different human tissues, such as placenta and liver.