Compendium of the most significant studies with reference to properties, intake, effects.

Growdon JH, Nader TM, Schoenfeld J, Wurtman RJ. L-threonine in the treatment of spasticity. Clin Neuropharmacol. 1991 Oct;14(5):403-12. doi: 10.1097/00002826-199110000-00003.

Abstract. Preclinical data indicate that the administration of the amino acid L-threonine increases glycine levels in rat spinal cord. In order to investigate glycinergic mechanisms in spasticity, and other signs of the upper motor syndrome, we gave 4.5 and 6.0 g/day of L-threonine to 18 patients with familial spastic paraparesis (FSP) according to a double-blind, crossover protocol. The response to treatment at the end of each 2-week period was based upon three measures: the physician's global impressions; the patients' global impressions; and semiquantitative ratings of strength, muscle tone, DTRs, walking, hopping, and running. Blood and CSF were collected during each treatment period for amino acid analyses. Based upon the severity rating scales, there was a statistically significant (p less than 0.02) decrease in motor impairment and spasticity during L-threonine administration compared to placebo treatment; significant treatment effects were not found on the physician's and patients' global impressions. Plasma and CSF levels of threonine increased significantly during L-threonine treatment but glycine levels did not change. These data indicate that L-threonine significantly suppressed the signs of spasticity even though the benefits were not clinically valuable.

Malinovsky AV. Why Threonine Is an Essential Amino Acid in Mammals and Birds: Studies at the Enzyme Level. Biochemistry (Mosc). 2018 Jul;83(7):795-799. doi: 10.1134/S0006297918070039. 

Abstract. In the review, we discuss why threonine is an essential amino acid in mammals and birds based on the pathways of threonine biosynthesis in these two classes of vertebrates.

Kumar Sahoo D, Devi Tulsiyan K, Jena S, Biswal HS. Implication of Threonine-Based Ionic Liquids on the Structural Stability, Binding and Activity of Cytochrome c. Chemphyschem. 2020 Dec 2;21(23):2525-2535. doi: 10.1002/cphc.202000761.

Abstract... , we disclose the molecular level understanding of the structural intactness and reactivity of a model protein cytochrome c (Cyt c) in biocompatible threonine-based ILs with the help of experimental techniques such as isothermal titration calorimetry (ITC), fluorescence spectroscopy, transmission electron microscopy (TEM) as well as molecular docking.

Chapman KP, Courtney-Martin G, Moore AM, Ball RO, Pencharz PB. Threonine requirement of parenterally fed postsurgical human neonates. Am J Clin Nutr. 2009 Jan;89(1):134-41. doi: 10.3945/ajcn.2008.26654. 

Abstract. The objective was to determine the parenteral threonine requirement for human neonates by using the minimally invasive indicator amino acid oxidation technique with L-[1-(13)C]phenylalanine as the indicator amino acid.

Rosenthal RG, Vögeli B, Wagner T, Shima S, Erb TJ. A conserved threonine prevents self-intoxication of enoyl-thioester reductases. Nat Chem Biol. 2017 Jul;13(7):745-749. doi: 10.1038/nchembio.2375.

Abstract.  We show that a single conserved threonine is essential to suppress the formation of a side product that would otherwise act as a high-affinity inhibitor of the enzyme. Substitution of this threonine with isosteric valine increases side-product formation by more than six orders of magnitude, while decreasing turnover frequency by only one order of magnitude.

Janssen PH. Propanol as an end product of threonine fermentation. Arch Microbiol. 2004 Dec;182(6):482-6. doi: 10.1007/s00203-004-0732-y.

Abstract. Clostridium sp. strain 17cr1 was able to ferment L-threonine to propionate and propanol. Electrons arising in the oxidation of 2-oxobutyrate to propionyl-CoA were apparently used in reductive pathway leading to propanol formation. Part of the propionyl-CoA was used to form propionate in an ATP-forming pathway via a propionate kinase, so that the final ATP yield was 0.5 mol per mol of L-threonine metabolised. Other growth substrates were fermented mainly to acetate and butyrate, and the reductive formation of butyrate, from 2 mol of acetyl-CoA or from crotonate or 3-hydroxybutyrate, was the main route for recycling reduced electron carriers arising during oxidative pathways for most substrates.

van der Sluis M, Schaart MW, de Koning BA, Schierbeek H, Velcich A, Renes IB, van Goudoever JB. Threonine metabolism in the intestine of mice: loss of mucin 2 induces the threonine catabolic pathway. J Pediatr Gastroenterol Nutr. 2009 Jul;49(1):99-107. doi: 10.1097/MPG.0b013e3181a23dbe.

Abstract. Previous studies have shown that the intestine uses a major part of the dietary threonine intake for the synthesis of the structural component of the protective intestinal mucus layer, the secretory mucin Muc2. In this context, the high intestinal demand for dietary threonine probably results from its incorporation into secretory mucins rich in threonine residues. Therefore, we compared threonine utilization in the colon of Muc2 knockout (Muc2-/-) and wild-type (Muc2+/+) mice to investigate the intestinal dietary threonine metabolism in the absence of Muc2, which results in inflammation of the colon.

Moundras C, Bercovici D, Rémésy C, Demigné C. Influence of glucogenic amino acids on the hepatic metabolism of threonine. Biochim Biophys Acta. 1992 Jan 23;1115(3):212-9. doi: 10.1016/0304-4165(92)90056-z. 

Abstract. The supplementation of a low-protein diet with L-threonine leads to a marked accumulation of threonine in plasma and liver, whereas increasing dietary protein generally leads to an induction of threonine dehydratase in the liver, hence depressed availability for extrasplanchnic tissues. The aim of the present study was, thus, to further investigate the factors which control the utilization of threonine by the liver.