(2S,3R)-2-Amino-3-(phosphonooxy)butanoic Acid

This compound is typically obtained as a white to off-white crystalline powder. Its molecular formula is C4H10NO6P, corresponding to a molecular weight of 199.10. It is highly soluble in water due to the presence of both amino and phosphate groups, and moderately soluble in polar organic solvents such as methanol and dimethyl sulfoxide. The molecule contains an amino acid backbone with a phosphate ester attached to the hydroxyl group of the side chain. The phosphate group is acidic and can exist in various protonation states depending on pH. The compound is hygroscopic and should be stored in tightly sealed containers under inert atmosphere at reduced temperature to prevent hydrolysis of the phosphate ester and absorption of moisture. It is stable under acidic conditions but may undergo dephosphorylation under strongly alkaline conditions or in the presence of phosphatases.

(2S,3R)-2-Amino-3-(phosphonooxy)butanoic acid, also known as O-phospho-L-threonine, is a phosphorylated amino acid derivative in which the hydroxyl group of L-threonine is esterified with phosphoric acid. The molecule retains the chiral centers of the parent amino acid, with the (2S,3R) configuration corresponding to the naturally occurring L-threonine stereochemistry. This phosphorylation introduces a dianionic phosphate group at physiological pH, conferring significant polarity and metal-binding capacity. As a key post-translational modification mimic, this compound serves as a model for understanding phosphoprotein structure and function. The phosphate moiety can engage in hydrogen bonding and electrostatic interactions with protein binding partners, while the amino acid backbone allows for incorporation into peptides and proteins. Its zwitterionic nature and multiple ionizable groups contribute to its complex pH-dependent behavior and solubility profile.

Biochemical Research Standard
This phosphorylated amino acid is widely employed as a reference standard in analytical biochemistry for identifying and quantifying phosphothreonine residues in proteins. It is used in chromatographic separations, mass spectrometry calibration, and enzymatic assays to study protein phosphorylation and dephosphorylation reactions. Researchers utilize it to validate analytical methods for phosphoamino acid analysis and to investigate substrate specificity of protein kinases and phosphatases.

Enzyme Substrate and Inhibitor Studies
In enzymology, this compound serves as a model substrate for studying phosphatases that specifically act on phosphothreonine residues. It is also used to investigate the binding interactions of phosphoprotein-binding domains such as forkhead-associated domains and WW domains, which recognize phosphorylated serine and threonine motifs. These studies provide insights into cellular signaling pathways and protein-protein interactions mediated by phosphorylation.

Peptide and Protein Synthesis
As a building block in solid-phase peptide synthesis, appropriately protected derivatives of this compound enable the incorporation of phosphorylated threonine residues into synthetic peptides. These phosphopeptides are essential tools for studying signal transduction, generating phosphospecific antibodies, and investigating the structural consequences of phosphorylation on protein conformation and function. The defined stereochemistry ensures faithful reproduction of natural phosphorylation sites.

Metabolic and Nutritional Research
In metabolic studies, this compound is used to investigate the metabolism of phosphorylated amino acids and their role in cellular phosphate homeostasis. It serves as a reference compound for studying the absorption, distribution, and excretion of phosphoamino acids in biological systems. Research involving bacterial and mammalian metabolism utilizes it to trace pathways of phosphate transfer and amino acid modification.