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Substrate specificity of human ceramide kinase.
Dayanjan S Wijesinghe1, Autumn Massiello, Preeti Subramanian
1Department of Biochemistry, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA.
Journal of Lipid Research
|September 20, 2005
Summary
Ceramide kinase (CERK) demonstrates high substrate specificity, requiring a minimum acyl chain length and specific structural features for activity. These findings clarify CERK
Area of Science:
- Biochemistry
- Enzymology
- Lipid Metabolism
Background:
- Ceramide kinase (CERK) is a key enzyme in eicosanoid synthesis.
- In vitro characterization of CERK's substrate specificity has been limited.
Purpose of the Study:
- To investigate the in vitro substrate specificity of human ceramide kinase (CERK).
- To elucidate the structural requirements for ceramide recognition by CERK.
Main Methods:
- Utilized baculovirus-expressed human CERK (6 x His).
- Employed a novel assay utilizing Triton X-100 mixed micelles for substrate analysis.
Main Results:
- CERK exhibits stereospecific recognition of ceramide.
- A minimum 12-carbon acyl chain and a 4-5 trans double bond are crucial for CERK activity.
- CERK shows high specificity for the sphingoid chain and the secondary amide group's free hydrogen.
- Phosphorylation occurs at the primary hydroxyl group, yielding ceramide-1-phosphate.
Conclusions:
- CERK possesses stringent substrate recognition properties, explaining its specific role in ceramide metabolism.
- These findings provide a detailed understanding of CERK's enzymatic mechanism and substrate binding requirements.