1-methylhistidine is derived from the dipeptide anserine (which consists of the amino acids 1-methylhistidine and beta-alanine). Anserine and its derivatives are associated with the consumption of poultry and fish. Both 1-methylhistidine and 3-methyl

Both 1-methylhistidine and 3-methylhistidine are histidine metabolites which have been proposed as markers of meat intake. Note that some confusion exists in the literature regarding the numbering of atoms in the imidazole ring of histidine &ndash

Alpha-Amino-N-butyric acid (α-ANB), also known as alphaaminobutyric acid, is a nonessential amino acid derived from the catabolism of methionine, threonine, and serine. α-ANB is both formed and metabolized by reactions which require vi

Alpha-aminoadipic acid (also known as 2-aminoadipic acid) is an intermediary biomarker of lysine and tryptophan metabolism. The further metabolism of alpha-aminoadipic acid to alpha-ketoadipic acid requires vitamin B6. Plasma alpha-aminoadipic aci

Alanine is a nonessential amino acid. It is the second most abundant amino acid in circulation, after glutamine. It is found in many foods including eggs, meat, lentils, and fish. Alanine is involved in sugar metabolism for energy and is import

Arginine is found in all protein foods and is very abundant in seeds and nuts. It is considered a semi-essential amino acid during early development, infection/inflammation, or renal and/or intestinal impairment. It has many functions in the body inc

Asparagine is a non-essential protein amino acid that is present in many fruits and vegetables including asparagus, from which it gets its name. Other dietary sources include meat, potatoes, eggs, nuts, and dairy. It can also be formed from aspart

Aspartic acid is a nonessential amino acid that plays roles in many important metabolic processes, such as energy production (citric acid cycle), hormone metabolism, CNS activation, and the urea cycle. It is found in many protein sources such as oyst

β-alanine is a breakdown product of carnosine and anserine, which are dipeptides from meat consumption. Although β-alanine’s properties are limited, its relationship to carnosine makes it important. Both have antioxidant properties. A

Beta-aminoisobutyric acid (also known as 3-aminoisobutyric acid) is a non-protein amino acid formed by the catabolism of valine and the nucleotide thymine. It is further catabolized to methylmalonic acid semialdehyde and propionyl-CoA. Levels are

Citrulline is an intermediate, nonprotein-forming amino acid in the urea cycle serving as a precursor to arginine. It derives its name from the watermelon (Citrullus vulgaris), where it was first isolated and identified. It is easily absorbed by t

Cysteine is a nonessential sulfur-containing amino acid. It is obtained from the diet and is also endogenously made from the intermediate amino acid cystathionine. Dietary cysteine sources include poultry, eggs, beef, and whole grains. This ami

Cystathionine is an intermediate dipeptide within the process of transsulfuration. Transsulfuration is the main route for irreversible homocysteine disposal, glutathione production, and energy. The initial step involves the enzyme cystathionine &b

Ethanolamine is an intermediary metabolite in the serine-to-choline sequence. It can be used to synthesize phosphatidylethanolamine (PE), a very important membrane phospholipid. Ethanolamine is not only a precursor, but also a breakdown product of PE

Gamma-aminobutyric acid (GABA) is an amino acid that functions as an inhibitory neurotransmitter. It serves one-third of brain neurons and is involved in depression and mania. Although there are some dietary supplement and food sources for GABA (c

Glutamic acid is a nonessential amino acid is derived from the diet and from the breakdown of gut proteins. Glutamate is a major excitatory neurotransmitter in the brain. It plays a role in neuronal differentiation, migration, and survival in the

Glutamine is a nonessential amino acid and is the most abundant amino acid in the body. It is formed from glutamate using the enzyme glutamine synthetase. Approximately 80% of glutamine is found in the skeletal muscle, and this concentration is 30

Glycine is a nonessential amino acid that is synthesized from choline, serine, hydroxyproline, and threonine. It has many important physiologic functions. It is one of three amino acids that make up glutathione. Glycine’s dietary sources inc

Histidine is a semi-essential amino acid which is formed in the breakdown of carnosine. Red meat is a common source of carnosine, and therefore histadine.  Other food sources include poultry, fish, nuts, seeds, and grains. Histidine and hista

Branched Chain Amino Acids (Isoleucine, Leucine, Valine) are the three branched chain amino acids (BCAAs). Branched chain amino acids (BCAA) are essential amino acids and must be obtained from the diet (mainly meat, grains, and dairy).  No

Branched Chain Amino Acids (Isoleucine, Leucine, Valine) Isoleucine, leucine and valine are the three branched chain amino acids (BCAAs). Branched chain amino acids (BCAA) are essential amino acids and must be obtained from the diet (mainly meat,

Lysine is a nutritionally essential amino acid abundant in meat, fish, fowl, and legumes and is needed for formation of body proteins and enzymes. Lysine can be methylated using S-adenosylmethionine (SAM) to synthesize carnitine, which is needed f

Methionine is an essential amino acid that plays an important role in the methylation cycle. Methionine is obtained from dietary intake or through homocysteine remethylation. Methionine’s dietary sources include eggs, fish, meats, Brazil nuts,

Ornithine is an intermediate nonprotein-forming amino acid of the urea cycle. Arginine is converted to ornithine via the arginase enzyme, with urea as a byproduct. Ornithine combined with carbamoyl phosphate is then converted into citrulline via t

Phenylalanine is an essential amino acid found in most foods which contain protein such as meat, fish, lentils, vegetables, and dairy.  Phenylalanine is the precursor to another amino acid, tyrosine. Because tyrosine is needed to form several

Phosphoethanolamine is an intermediate in the serineto-choline sequence. It is both a precursor and byproduct of phospholipid biosynthesis and breakdown. As a precursor to the phospholipid phosphatidylethanolamine, phosphoethanolamine plays a key rol

Phosphoserine is the phosphorylated ester of the amino acid serine. The addition of a phosphoryl group to an amino acid, or its removal, plays a role in cell signaling and metabolism. Phosphoserine is a byproduct of glycolysis and subsequent intermed

Proline is a nonessential amino acid. It contains a secondary α-imino group and is sometimes called an α-imino acid. Proline, and its metabolite hydroxyproline, constitute a third of the total amino acids found in collagen. Lysine, pro

Sarcosine is an amino acid made within the methylation cycle when S-adenosylmethionine (SAM) is conjugated with glycine. It can also be made by catabolism of dimethylglycine (DMG). There are many dietary sources of sarcosine including eggs, legume

Serine is found in soybeans, nuts, eggs, lentils, shellfish, and meats. Serine is a nonessential amino acid used in protein biosynthesis and can be derived from four possible sources: dietary intake, degradation of protein and phospholipids, biosy

Taurine differs from other amino acids because a sulfur group replaces the carboxyl group of what would be the nonessential amino acid, β-alanine. It takes part in biochemical reactions and is not fully incorporated into proteins. In most tis

Threonine is a large neutral amino acid and a precursor for the amino acid glycine. Foods that contain relatively high amounts of threonine include cheeses (especially Swiss), meat, fish, poultry, seeds, walnuts, cashews, almonds and peanuts. Thre

Tryptophan is involved in serotonin production via vitamin B6-dependent pathways resulting in the intermediate 5-hydroxytryptophan (5-HTP). 5-HTP is often used as a supplement for serotonin formation instead of tryptophan, which can be quickly metabo

Tyrosine is a conditionally essential amino acid which can come directly from the digestion of dietary protein. Common food sources include dairy, beans, whole grains, meat, and nuts. If intake is insufficient, tyrosine can be formed from the e

Urea is a nontoxic byproduct of nitrogen (ammonia) detoxification. It is formed in the liver via the urea cycle and is the end product of protein metabolism. It is essentially a waste product with no physiological function.

Branched Chain Amino Acids (Isoleucine, Leucine, Valine) Isoleucine, leucine and valine are the three branched chain amino acids (BCAAs). Branched chain amino acids (BCAA) are essential amino acids and must be obtained from the diet (mainly meat,