Model Analysis of the Apparent Saturation Kinetics of Purine Nucleobase Uptake in Cells co-Expressing Transporter and Metabolic Enzyme.
Pharm Res
; 38(9): 1585-1592, 2021 Sep.
Article
en En
| MEDLINE
| ID: mdl-34435306
PURPOSE: This study aims to understand the effect of salvage enzyme activity on the saturable kinetics of facilitated cellular uptake of purine nucleobase by developing a cellular kinetic model incorporating equilibrative nucleobase transporter 1 (ENBT1) and adenine phosphoribosyltransferase (APRT), with adenine as a model nucleobase. METHODS: A cellular kinetic model incorporating the functions of ENBT1 and APRT was developed using Napp software and employed for model-based analysis of the cellular disposition of adenine. RESULTS: Simulation analysis using the developed cellular kinetic model could account for the experimentally observed time-dependent changes in the Km(app) value of adenine for ENBT1-mediated uptake. At a long experimental time, the model shows that uptake of adenine is rate-limited by APRT, enabling determination of the Km value for APRT. At early time, the rate-limiting step for adenine uptake is ENBT1-mediated transport, enabling determination of the Km value for ENBT1. Further simulations showed that the effect of experimental time on the Km(app) value for ENBT1-mediated uptake is dependent on the APRT expression level. CONCLUSION: Our findings indicate that both enzyme expression levels and experimental time should be considered when using cellular uptake studies to determine the Km values of purine nucleobases for facilitated transporters.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Purinas
/
Transporte Biológico
/
Proteínas de Transporte de Nucleósido Equilibrativas
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Revista:
Pharm Res
Año:
2021
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Estados Unidos