L-tyrosine

Identity resolution

Record the claimed structure and evidence capable of excluding the relevant tyrosine alternatives.

1. Does the reference identity specify para-hydroxyphenylalanine with the L configuration? definition
2. Which measurements distinguish this sample from D-tyrosine, DL-tyrosine and other hydroxyl-position isomers? measurement
3. Which identity claims rely only on a label or certificate rather than a sample-specific test? provenance

Molecular context boundary

Record whether the observation concerns free L-tyrosine, a specified ionic preparation or tyrosine incorporated into another entity.

1. Is the material free L-tyrosine, a counterion-containing preparation, a covalent derivative or a bound residue? boundary
2. Was the reported tyrosine present before analysis, or released by hydrolysis during sample preparation? provenance
3. Which related model owns any derivative, protein or finished formulation associated with this record? boundary

Interpretable content

Require a selective assay, explicit reporting basis and representative sampling for each content value.

1. Does the assay measure L-tyrosine specifically, total tyrosine or a less selective response? measurement
2. Is content reported on an as-received, dried or other corrected basis, and what corrections were applied? measurement
3. Which sample, reference standard and calibration establish the reported result? provenance

Resolved impurity profile

Record identified impurities, unresolved signals and the limits of the methods used.

1. What limits or measured values are available for D-tyrosine, related amino acids and positional isomers? measurement
2. Which process contaminants or residual solvents were tested, and which remain unassessed? measurement
3. Do unresolved peaks or insufficient detection limits require additional testing before the proposed use? action

Weighable and representative material

Record water content, particle presentation and heterogeneity when they affect assay or preparation.

1. What water-content or drying evidence supports the mass basis used for this L-tyrosine solid? measurement
2. Are caking, particle-size differences or visible heterogeneity affecting sampling or dissolution? measurement
3. Does the intended operation require solid-form identification or particle-size control beyond the available evidence? action

Verified solution state

Keep nominal loading, dissolved concentration and the effects of acid or base additions explicit.

1. At what solvent composition, pH and temperature was the preparation made and assessed? measurement
2. Is the stated concentration based on material added or measured dissolved L-tyrosine, and is undissolved material present? measurement
3. If acid or base was added, what counterions and final conditions must be recorded before using the preparation? action

Traceable tyrosine material

Maintain the lineage linking supplier material, tested samples and derived aliquots or solutions.

1. Which supplier lot and certificate apply to this material, and do they explicitly identify L-tyrosine? provenance
2. What is known about the production and purification route that could guide impurity testing? provenance
3. Which dissolution, filtration, drying or other processing steps separate this material from the tested lot? provenance

Condition supported by evidence

Record storage conditions and changes without assigning an unsupported universal shelf life.

1. What temperature, moisture, light and container exposure history is documented for the solid or solution? provenance
2. Have colour, precipitation, assay or impurity results changed relative to an established baseline? measurement
3. Which documented excursion or change triggers retesting, quarantine or disposal under the applicable specification? action

Use-bound eligibility

Attach eligibility to a named use, an explicit specification and the evidence satisfying it.

1. Is the material intended as an analytical standard, synthesis input, culture-medium component or formulation ingredient? definition
2. Which identity, stereochemical purity, content and contamination requirements apply to that use? boundary
3. Which unmet or untested requirement prevents release for the intended operation? action

Evidence-based material action

Record the calculation and operating references supporting a proposed handling or preparation step.

1. What mass or volume supplies the requested L-tyrosine amount after accounting for assay basis and measured concentration? measurement
2. Which material-specific safety data and procedure govern weighing, transfer, preparation and waste handling? action
3. Does the request concern material handling, or must a patient-specific administration decision be routed to a clinical model? boundary

Kinds and varieties

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Free crystalline L-tyrosine (food, feed, pharmacopeial and supplement grades)
• Protein residue Tyr/Y in polypeptides
• N-acetyl-L-tyrosine (soluble parenteral-nutrition form)
• D-tyrosine and DL-tyrosine (enantiomer and racemate)
• para-tyrosine versus meta- and ortho-tyrosine (ring positional isomers)
• O-phospho-L-tyrosine (post-translational modification)
• 3-iodo- and 3,5-diiodo-L-tyrosine (thyroid-hormone intermediates)
• 3-nitrotyrosine (nitrative-stress marker)

1. Which of these kinds and varieties hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Identifiers and schemes

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Wikidata - Q188017 - item L-tyrosine
• CAS Registry Number - 60-18-4 - L-enantiomer; DL-tyrosine is 556-03-6
• PubChem CID - 6057 - L-Tyrosine
• ChEBI - CHEBI:17895 - L-tyrosine; secondary IDs include CHEBI:46161
• InChIKey - OUYCCCASQSFEME-QMMMGPOBSA-N - stereospecific L-key; racemate key is OUYCCCASQSFEME-UHFFFAOYSA-N
• UNII - 42HK56048U - FDA Global Substance Registration System
• EC / EINECS - 200-460-4 - ECHA InfoCard 100.000.419
• IUPAC/IUBMB residue codes - Tyr / Y - three-letter and one-letter protein codes; mRNA codons UAC and UAU
• KEGG COMPOUND - C00082 - L-Tyrosine
• HMDB - HMDB0000158 - also HMDB0000647
• DrugBank - DB00135 - tyrosine
• EPA CompTox - DTXSID1023730 - DSSTox substance id

1. Which of these identifiers and schemes hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Standards and regulation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• USP-NF monograph Tyrosine (United States Pharmacopeial Convention): NLT 98.5% and NMT 101.5% l-tyrosine on the dried basis
• Ph. Eur. monograph 1161 Tyrosine (EDQM): 99.0-101.0% dried substance, product of fermentation or protein hydrolysis
• Food Chemicals Codex monograph l-Tyrosine (USP FCC)
• EFSA FEEDAP Scientific Opinion (EFSA Journal 2013;11(7):3310) on L-tyrosine as a feed additive for all animal species
• EU feed-additive authorisation following that opinion (European Commission / EFSA)
• US Dietary Supplement Health and Education Act of 1994 (FDA): amino acids may be marketed as dietary supplements without premarket approval of efficacy
• Norwegian VKM 2016 risk assessment of L-tyrosine as an "other substance" in food supplements (Norwegian Scientific Committee for Food Safety)
• REACH/CLP listing under EC 200-460-4 (ECHA); TSCA listing in the United States (EPA)

1. Which of these standards and regulation hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Real-world use

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Residue in essentially all proteins and in recombinant biologics; one of the 20 standard coded amino acids
• Oral dietary-supplement powder or capsules, typically taken before acute stress or cognitive load
• Component of intravenous amino-acid solutions for parenteral nutrition; free tyrosine is poorly soluble so N-acetyl-L-tyrosine is often used instead
• Conditionally essential nutrient in phenylketonuria, where conversion from phenylalanine is blocked
• Feed additive, including to support melanin-dependent coat colour in cats
• Ingredient in cell-culture media and a starting material for peptide synthesis
• Industrial precursor manufactured by protein hydrolysis (historically feather keratin) or by fermentation with engineered microbes
• Clinical laboratory analyte in plasma/urine amino-acid profiles and in the work-up of tyrosinemia and PKU

1. Which of these real-world use hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Typical measurements

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• molar mass - 181.19 - g·mol⁻¹
• water solubility of the free acid - about 0.45 at 25 °C (Ph. Eur. very slightly soluble); FCC states 1 g in about 230 mL - g·L⁻¹
• specific optical rotation [α] (USP: 50 mg·mL⁻¹ in 1 N HCl) - −9.8 to −11.2 - °
• melting / decomposition - >300 (decomposition) - °C
• pharmacopeial assay (dried substance) - 98.5-101.5 (USP); 99.0-101.0 (Ph. Eur.) - %
• loss on drying (105 °C) - NMT 0.3 (USP); max 0.5 (Ph. Eur.) - %
• common labeled oral supplement dose - 500-2000 - mg·day⁻¹
• EFSA-considered safe feed inclusion - 0.5 of diet (food-producing animals); 1.5 (non-food-producing animals) - %

1. Which of these typical measurements hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Failure modes and hazards

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Inborn errors of tyrosine catabolism (tyrosinemia types I-III) cause hepatic, renal and oculocutaneous injury from tyrosine and metabolite accumulation
• Excess dietary tyrosine in animals can depress growth and cause eye lesions; EFSA flags behavioural changes in young animals at high inclusion
• Norwegian VKM judged 1250-2000 mg/day in food supplements as a possible health risk across age groups
• Very low water solubility of the free acid causes precipitation in liquid formulations and complicates parenteral nutrition unless an acetylated form is used
• EFSA, in the absence of data, treated the feed-grade hydrolysate as potentially irritating to skin and eyes, a potential dermal sensitiser, and hazardous by inhalation
• In PKU, inadequate tyrosine intake follows from blocked phenylalanine hydroxylation
• Phenol side-chain oxidation (dityrosine, DOPA, quinones, nitrotyrosine) degrades protein quality and is a stress biomarker rather than a benign impurity

1. Which of these failure modes and hazards hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Regional variation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Commerce and US supplement labels usually say L-Tyrosine; Ph. Eur./BP titles the monograph Tyrosine and require the L-configuration by specific rotation
• US marketing as a dietary supplement under DSHEA versus EU treatment as a food-supplement "other substance" and as an authorised feed additive after EFSA
• Parenteral-nutrition practice commonly substitutes N-acetyl-L-tyrosine for free L-tyrosine because of solubility; formula composition still differs by region and product
• Norwegian risk assessment is more cautious on high-dose supplements than the open US supplement market
• Industrial origin is specified in Ph. Eur. as fermentation or protein hydrolysis; the 2013 EFSA dossier was a feather-keratin acid hydrolysate

1. Which of these regional variation hold for the sense of L-tyrosine this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• L-phenylalanine - Lacks the para-phenolic hydroxyl; precursor via phenylalanine hydroxylase. Separate by HPLC retention, UV maximum (Tyr ~275 nm vs Phe ~258 nm) and the 4-OH in the molecular formula.
• L-DOPA (3,4-dihydroxy-L-phenylalanine) - Extra ring hydroxyl (catechol). Distinguish by mass +16 Da versus tyrosine, catechol colour tests, and its use as a dopamine-replacement drug rather than a proteinogenic residue.
• D-tyrosine - Opposite α-carbon configuration (CAS 556-02-5). Chiral HPLC or USP/Ph. Eur. specific rotation in acid (L is levorotatory, about −10°) separates the enantiomers.
• DL-tyrosine - Racemate, CAS 556-03-6, InChIKey OUYCCCASQSFEME-UHFFFAOYSA-N. Optical inactivity plus the racemic InChIKey distinguish it from L-tyrosine.
• m-tyrosine and o-tyrosine - Hydroxyl at ring position 3 or 2 rather than 4; arise from non-enzymatic radical hydroxylation of phenylalanine. Reverse-phase HPLC and aromatic ¹H NMR chemical shifts separate the regioisomers.
• N-acetyl-L-tyrosine - N-acetylated, much more water-soluble parenteral form; MS +42 Da and different pharmacopeial identity. It is not equivalent on a molar basis as a plasma-tyrosine source.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of L-tyrosine this model covers, and on what evidence? provenance