Metabolic intermediate

Metabolic intermediates are molecules which are the precursors or metabolites of biologically significant molecules.

Although these intermediates are of relatively minor direct importance to cellular function, they can play important roles in the allosteric regulation of enzymes.

Clinical significance

Some can be useful in measuring rates of metabolic processes (for example, 3,4-dihydroxyphenylacetic acid or 3-aminoisobutyrate).

Because they can represent unnatural points of entry into natural metabolic pathways, some (such as AICA ribonucleotide) are of interest to researchers in developing new therapies.

to HMG-CoA	Acetyl-CoA Acetoacetyl-CoA HMB HMB-CoA HMG-CoA

Ketone bodies	Acetone Acetoacetic acid β-Hydroxybutyric acid

to DMAPP	Mevalonic acid Phosphomevalonic acid 5-Diphosphomevalonic acid Isopentenyl pyrophosphate Dimethylallyl pyrophosphate

Geranyl-	Geranyl pyrophosphate Geranylgeranyl pyrophosphate

Carotenoid	Prephytoene diphosphate Phytoene

Non-mevalonate pathway

To Cholesterol

From Cholesterol
(to steroids)

Steroid hormones

See here instead.

Nonhuman

Phytosterols	Stigmasterol Brassicasterol

Ergosterols	Ergosterol Ergocalciferol

Amino acid metabolism metabolic intermediates

K→acetyl-CoA

lysine→	Saccharopine Allysine α-Aminoadipic acid α-Ketoadipate Glutaryl-CoA Glutaconyl-CoA Crotonyl-CoA β-Hydroxybutyryl-CoA

leucine→	α-Ketoisocaproic acid β-hydroxy β-methylbutyric acid β-hydroxy β-methylbutyryl-CoA Isovaleryl-CoA 3-Methylcrotonyl-CoA 3-Methylglutaconyl-CoA HMG-CoA

tryptophan→alanine→	N'-Formylkynurenine Kynurenine Anthranilic acid 3-Hydroxykynurenine 3-Hydroxyanthranilic acid 2-Amino-3-carboxymuconic semialdehyde 2-Aminomuconic semialdehyde 2-Aminomuconic acid Glutaryl-CoA

G→pyruvate→citrate

glycine→serine→	3-Phosphoglyceric acid glycine→creatine: Glycocyamine Phosphocreatine Creatinine

G→glutamate→
α-ketoglutarate

histidine→	Urocanic acid Imidazol-4-one-5-propionic acid Formiminoglutamic acid Glutamate-1-semialdehyde

proline→	1-Pyrroline-5-carboxylic acid

arginine→	Agmatine Ornithine Citrulline Cadaverine Putrescine

other	cysteine+glutamate→glutathione: γ-Glutamylcysteine

G→propionyl-CoA→
succinyl-CoA

valine→	α-Ketoisovaleric acid Isobutyryl-CoA Methacrylyl-CoA 3-Hydroxyisobutyryl-CoA 3-Hydroxyisobutyric acid 2-Methyl-3-oxopropanoic acid

isoleucine→	2,3-Dihydroxy-3-methylpentanoic acid 2-Methylbutyryl-CoA Tiglyl-CoA 2-Methylacetoacetyl-CoA

methionine→	generation of homocysteine: S-Adenosyl methionine S-Adenosyl-L-homocysteine Homocysteine conversion to cysteine: Cystathionine alpha-Ketobutyric acid+Cysteine

threonine→	α-Ketobutyric acid

propionyl-CoA→	Methylmalonyl-CoA

G→fumarate

phenylalanine→tyrosine→	4-Hydroxyphenylpyruvic acid Homogentisic acid 4-Maleylacetoacetic acid

G→oxaloacetate

see urea cycle

Other

Cysteine metabolism	Cysteine sulfinic acid

Nucleotide metabolic intermediates

Purine metabolism

Anabolism

R5P→IMP:	R5P PRPP PRA GAR FGAR FGAM AIR CAIR SAICAR AICAR FAICAR

IMP→AMP:	Adenylosuccinate

IMP→GMP:	Xanthosine monophosphate

Catabolism

Pyrimidine metabolism

Anabolism

Catabolism

uracil:	Dihydrouracil 3-Ureidopropionic acid β-Alanine

thymine:	Dihydrothymine β-Ureidoisobutyric acid 3-Aminoisobutyric acid

Neurotransmitter metabolic intermediates

catecholamines

Anabolism
(tyrosine→epinephrine)

Tyrosine → Levodopa → Dopamine → Norepinephrine → Epinephrine

Catabolism/
metabolites

dopamine:	DOPAL DOPAC MOPET Hydroxytyrosol 3-Methoxytyramine Homovanillic acid

norepinephrine:	3,4-Dihydroxymandelic acid Normetanephrine Vanillylmandelic acid 3-Methoxy-4-hydroxyphenylglycol Dihydroxyphenylethylene glycol

epinephrine:	Metanephrine

tryptophan→serotonin

anabolism:	5-Hydroxytryptophan

catabolism:	5-Hydroxyindoleacetic acid

serotonin→melatonin

Normelatonin

Heme metabolic intermediates

Porphyrin biosynthesis

early mitochondrial:	D-Aminolevulinic acid

cytosolic:	Porphobilinogen Hydroxymethylbilane Uroporphyrinogen III Coproporphyrinogen III

late mitochondrial:	Protoporphyrinogen IX Protoporphyrin IX

Heme degradation
and excretion

Breakdown of heme

spleen:	Heme → Biliverdin → Bilirubin

blood:	Bilirubin+Albumin

liver:	Bilirubin diglucuronide

Intestine, excretion in feces

Kidney, excretion in urine

Urobilin

Thyroid hormone metabolic intermediates

Tyrosine / iodotyrosine	Monoiodotyrosine Diiodotyrosine

Thyronine / iodothyronine	3'-Monoiodothyronine 3,3'-Diiodothyronine 3,5-Diiodothyronine 3,3',5-Triiodothyronine (T₃) 3,3',5'-Triiodothyronine (Reverse T₃) 3,5,3',5'-Tetraiodothyronine (Thyroxine, T₄)

Thyronamine / iodothyronamine	3-Iodothyronamine 3,3',5-Triiodothyronamine

Iodothyroacetate / iodothyroacetic acid	Triiodothyroacetate (TRIAC)

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Glycogenesis and glycogenolysis metabolic intermediates

Glucose	Glucose 6-phosphate Glucose 1-phosphate

Uridine	Uridine diphosphate glucose Uridine triphosphate

Other	Glycogen Limit dextran

Pentose phosphate pathway metabolic intermediates

Oxidative	6-Phosphogluconolactone 6-Phosphogluconate Ribulose 5-phosphate Ribose 5-phosphate

Nonoxidative	Xylulose 5-phosphate Sedoheptulose 7-phosphate Erythrose 4-phosphate

Metabolic intermediate

Clinical significance

See also