Theoretical analysis of carbon-13 magnetization transfer for in vivo exchange between α-ketoglutarate and glutamate

✍ Scribed by Jun Shen; Su Xu

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 141 KB
• Volume: 19
• Category: Article
• ISSN: 0952-3480
• DOI: 10.1002/nbm.1021

✦ Synopsis

Abstract

Many enzymes catalyze fast exchange between a small pool and a large pool in vivo. For example, aspartate aminotransferase catalyzes fast exchanges between α‐ketoglutarate and glutamate and between oxaloacetate and aspartate, which can be detected using in vivo^13^C MRS while saturating α‐carbons of the keto acids. Unlike in the traditional saturation transfer experiments studied using ^31^P MRS, the tricarboxylic acid cycle intermediates α‐ketoglutarate and oxaloacetate are below the detection limit of in vivo NMR. In this work, a theoretical analysis of the saturation transfer between α‐ketoglutarate and glutamate catalyzed by aspartate aminotransferase was presented to examine the requirements for complete saturation of the rapidly turning over α‐ketoglutarate pool without affecting the longitudinal magnetization of glutamate. The fast turnover of the small α‐ketoglutarate pool also allows a quasi‐steady‐state approximation of its dynamic longitudinal relaxation. The theoretical analysis provides a useful guide for designing experimental methods to characterize saturation transfer processes associated with fast turning over small pools in vivo. Copyright © 2006 John Wiley & Sons, Ltd.