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Variations in elastaselike esterase activities in human leucocytes during cell maturation.
Summary
Human leucocyte granules contain elastase isozymes and less-characterized elastase-like esterases (SE). SE may be a precursor to elastase isozymes, found in immature cells and present in bone marrow granules.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Human peripheral blood leucocytes contain multiple elastase isozymes.
- Associated with these are slow-moving elastase-like esterases (SE) with poorly understood characteristics.
Purpose of the Study:
- To characterize the slow-moving elastase-like esterases (SE) found in human leucocyte granules.
- To investigate the relationship between SE and known elastase isozymes.
Main Methods:
- Enzyme activity assays using synthetic substrates (Ac-DL-Ala-1-ONap, Boc-Ala-ONp) with and without Triton.
- Cationic electrophoresis at pH 4.3.
- Inhibition studies using Diisopropylfluorophosphate (Dip-F) and Ac-(Ala)2-Pro-AlaCH2Cl.
- Immunochemical analysis.
- Analysis of leucocyte granules from nonleukemic bone marrow.
Main Results:
- SE hydrolyze elastase substrates, but migrate differently on gels and require Triton for optimal activity, unlike elastase isozymes.
- Both SE and elastase isozymes are inactivated by Dip-F, but only elastase isozymes are inhibited by Ac-(Ala)2-Pro-AlaCH2Cl.
- Immunochemical studies show cross-reactivity between SE and elastase isozymes.
- Bone marrow granules contain SE but lack active elastase isozymes.
Conclusions:
- SE exhibit distinct properties from mature elastase isozymes.
- SE may represent a precursor or zymogen form of leucocyte elastase isozymes.
- This precursor form is present in immature cells and bone marrow granules.