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Published on: October 4, 2017
Specificity of gamma-glutamyl cyclotransferase
Canadian Journal of Biochemistry
|June 1, 1975
Summary
Researchers synthesized 18 carbon-14 labeled gamma-L-glutamyl peptides using the phthaloyl method. A novel method using gamma-glutamyl cyclotransferase was developed to determine D-isomer impurities and prepare pure gamma-D-glutamyl peptides.
Area of Science:
- Biochemistry
- Organic Chemistry
- Enzymology
Background:
- Gamma-L-glutamyl peptides are important in biological systems.
- Accurate synthesis and purification of these peptides are crucial for research.
- Distinguishing between L- and D-glutamyl isomers is essential for biochemical studies.
Purpose of the Study:
- To synthesize and characterize 18 novel gamma-L-glutamyl peptides labeled with carbon-14.
- To develop and validate a new method for quantifying D-glutamyl isomers in synthetic peptides.
- To investigate the substrate specificity of gamma-glutamyl cyclotransferase for potential preparative applications.
Main Methods:
- Synthesis of gamma-L-glutamyl peptides using the phthaloyl method.
- Isolation and purification using Dowex-1 column chromatography and high-voltage electrophoresis.
- Quantification of D-glutamyl isomers via glutamic decarboxylase or gamma-glutamyl cyclotransferase digestion.
- Enzymatic assays with purified pig liver gamma-glutamyl cyclotransferase and tissue extracts.
Main Results:
- Successfully synthesized 18 carbon-14 labeled gamma-L-glutamyl peptides.
- Identified minor impurities of corresponding D-glutamyl isomers in synthetic products.
- Established that gamma-glutamyl cyclotransferase stereoselectively acts on L-glutamyl substrates.
- Demonstrated the enzyme's utility for preparing gamma-D-glutamyl peptides from racemic mixtures.
- Characterized the structural requirements for gamma-glutamyl cyclotransferase substrates, emphasizing the L-configuration of the linked amino acid.
Conclusions:
- The phthaloyl method is effective for synthesizing labeled gamma-L-glutamyl peptides.
- Gamma-glutamyl cyclotransferase is a specific enzyme that can be used for both analytical and preparative purposes in peptide chemistry.
- The L-configuration of the amino acid linked to the gamma-glutamyl group is a critical determinant of substrate recognition by gamma-glutamyl cyclotransferase.
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