QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lamers, Y. Articles by Gregory, J. F. Search for Related Content PubMed PubMed Citation Articles by Lamers, Y. Articles by Gregory, J. F., III

---

Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Glycine Turnover and Decarboxylation Rate Quantified in Healthy Men and Women Using Primed, Constant Infusions of [1,2-¹³C₂]Glycine and [²H₃]Leucine^1,2

³ Food Science and Human Nutrition Department, Institute of Food and Agricultural Sciences; ⁴ Division of Endocrinology and Metabolism, Department of Medicine; and ⁵ Department of Biochemistry and Molecular Biology, College of Medicine, University of Florida, Gainesville, FL 32611-0370

^* To whom correspondence should be addressed. E-mail: jfgy{at}ufl.edu.

Glycine plays several roles in human metabolism, e.g. as a 1-carbon donor, in purine synthesis, and as a component of glutathione. Glycine is decarboxylated via the glycine cleavage system (GCS) that yields concurrent generation of a 1-carbon unit as 5,10-methylenetetrahydrofolate (methyleneTHF). Serine hydroxymethyltransferase (SHMT) catalyzes the interconversion of glycine and serine, another 1-carbon donor. The quantitative role of glycine in human 1-carbon metabolism has received little attention. The aim of this protocol was to quantify whole body glycine flux, glycine to serine flux, and rate of glycine cleavage in humans. A primed, constant infusion with 9.26 µmol·kg^–1·h^–1 [1,2-¹³C₂]glycine and 1.87 µmol·kg^–1·h^–1 [²H₃]leucine was used to quantify the kinetic behavior of glycine in young, healthy volunteers (n = 5) in a fed state. The isotopic enrichment of infused tracers and metabolic products in plasma, as well as breath ¹³CO₂ enrichment, were determined for use in kinetic analysis. Serine synthesis by direct conversion from glycine via SHMT occurred at 193 ± 28 µmol·kg^–1·h^–1 (mean ± SEM), which comprised 41% of the 463 ± 55 µmol·kg^–1·h^–1 total glycine flux. Nearly one-half (46%) of the glycine-to-serine conversion occurred using GCS-derived methyleneTHF 1-carbon units. Based on breath ¹³CO₂ measurement, glycine decarboxylation (190 ± 41 µmol·kg^–1·h^–1) accounted for 39 ± 6% of whole body glycine flux. This study is the first to our knowledge to quantify human glycine cleavage and glycine-to-serine SHMT kinetics. GCS is responsible for a substantial proportion of whole body glycine flux and constitutes a major route for the generation of 1-carbon units.

This article has been cited by other articles:

				S. Dasarathy, T. Kasumov, J. M. Edmison, L. L. Gruca, C. Bennett, C. Duenas, S. Marczewski, A. J. McCullough, R. W. Hanson, and S. C. Kalhan Glycine and urea kinetics in nonalcoholic steatohepatitis in human: effect of intralipid infusion Am J Physiol Gastrointest Liver Physiol, September 1, 2009; 297(3): G567 - G575. [Abstract] [Full Text] [PDF]

				Y. Lamers, B. O'Rourke, L. R Gilbert, C. Keeling, D. E Matthews, P. W Stacpoole, and J. F Gregory III Vitamin B-6 restriction tends to reduce the red blood cell glutathione synthesis rate without affecting red blood cell or plasma glutathione concentrations in healthy men and women Am. J. Clinical Nutrition, August 1, 2009; 90(2): 336 - 343. [Abstract] [Full Text] [PDF]

				Y. Lamers, J. Williamson, D. W. Theriaque, J. J. Shuster, L. R. Gilbert, C. Keeling, P. W. Stacpoole, and J. F. Gregory III Production of 1-Carbon Units from Glycine Is Extensive in Healthy Men and Women J. Nutr., April 1, 2009; 139(4): 666 - 671. [Abstract] [Full Text] [PDF]

				H. F. Nijhout, J. F. Gregory, C. Fitzpatrick, E. Cho, K. Y. Lamers, C. M. Ulrich, and M. C. Reed A Mathematical Model Gives Insights into the Effects of Vitamin B-6 Deficiency on 1-Carbon and Glutathione Metabolism J. Nutr., April 1, 2009; 139(4): 784 - 791. [Abstract] [Full Text] [PDF]

				Y. Lamers, J. Williamson, M. Ralat, E. P. Quinlivan, L. R. Gilbert, C. Keeling, R. D. Stevens, C. B. Newgard, P. M. Ueland, K. Meyer, et al. Moderate Dietary Vitamin B-6 Restriction Raises Plasma Glycine and Cystathionine Concentrations While Minimally Affecting the Rates of Glycine Turnover and Glycine Cleavage in Healthy Men and Women J. Nutr., March 1, 2009; 139(3): 452 - 460. [Abstract] [Full Text] [PDF]