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Updated: Jul 15, 2026
07:59
Functional Characterization of Endogenously Expressed Human RYR1 Variants
Published on: June 9, 2021
Functional characterization of two novel CYP2C19 variants (CYP2C19*18 and CYP2C19*19) found in a Japanese population
Summary
Genetic variations in Cytochrome P450 2C19 (CYP2C19) affect drug metabolism. The CYP2C19*19 variant, with a Ser51Gly substitution, shows reduced S-mephenytoin metabolism, impacting drug response.
Area of Science:
- Pharmacogenomics
- Enzyme kinetics
- Drug metabolism
Background:
- Cytochrome P450 2C19 (CYP2C19) is crucial for metabolizing numerous drugs.
- Genetic variations (polymorphisms) in CYP2C19 lead to significant differences in drug metabolic activity among individuals.
- Previously identified variants CYP2C19*18 and CYP2C19*19 possess specific amino acid substitutions.
Purpose of the Study:
- To investigate the functional impact of amino acid substitutions in CYP2C19 variants.
- To precisely determine the effect of Arg329His/Ile331Val (in CYP2C19*18) and Ser51Gly/Ile331Val (in CYP2C19*19) on CYP2C19 enzyme activity.
- To compare the S-mephenytoin 4'-hydroxylation activity of wild-type and variant CYP2C19 proteins.
Main Methods:
- Heterologous expression of wild-type (CYP2C19.1B) and variant (CYP2C19.18, CYP2C19.19) CYP2C19 proteins in yeast cells.
- Determination of S-mephenytoin 4'-hydroxylation activities for each expressed protein.
- Enzyme kinetic analysis, including determination of K(m) and V(max) values, to assess substrate affinity and catalytic efficiency.
Main Results:
- CYP2C19.19 exhibited a significantly higher K(m) (3.0-fold) for S-mephenytoin 4'-hydroxylation compared to CYP2C19.1B.
- No significant differences in V(max) were observed between CYP2C19.1B and CYP2C19.19 when normalized for protein levels.
- The V(max)/K(m) values for CYP2C19.19 were substantially reduced (29-47%) compared to CYP2C19.1B, indicating decreased substrate affinity. CYP2C19.18 showed similar kinetic parameters to CYP2C19.1B.
Conclusions:
- The Ser51Gly substitution in CYP2C19.19 significantly reduces the enzyme's affinity for S-mephenytoin.
- CYP2C19*19 genetic polymorphism is likely to contribute to interindividual variability in the clinical response to drugs metabolized by CYP2C19.
- The CYP2C19*18 variant did not show significant functional differences compared to the wild-type in this assay.
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