β-Hydroxy β-methylbutyryl-CoA

(Redirected from HMB-CoA)

β-Hydroxy β-methylbutyryl-CoA
Names

IUPAC name 3′-O-Phosphonoadenosine 5′-ethyl}amino)-3-oxopropyl]amino}-2,2-dimethyl-4-oxobutyl dihydrogen diphosphate]
Systematic IUPAC name O-{methyl} O-ethyl}amino)-3-oxopropyl]amino}-2,2-dimethyl-4-oxobutyl] dihydrogen diphosphate
Other names β-hydroxyisovaleryl-CoA 3-hydroxyisovaleryl-CoA 3-hydroxy-3-methylbutyryl-CoA
Identifiers
3D model (JSmol)	Interactive image
ChEBI	CHEBI:28291
ChemSpider	10140181
KEGG	C05998
PubChem CID	11966188
CompTox Dashboard (EPA)	DTXSID001336036
InChI InChI=1S/C26H44N7O18P3S/c1-25(2,20(37)23(38)29-6-5-15(34)28-7-8-55-16(35)9-26(3,4)39)11-48-54(45,46)51-53(43,44)47-10-14-19(50-52(40,41)42)18(36)24(49-14)33-13-32-17-21(27)30-12-31-22(17)33/h12-14,18-20,24,36-37,39H,5-11H2,1-4H3,(H,28,34)(H,29,38)(H,43,44)(H,45,46)(H2,27,30,31)(H2,40,41,42)/t14-,18-,19-,20+,24-/m1/s1Key: PEVZKILCBDEOBT-CITAKDKDSA-N
SMILES CC(C)(CC(=O)SCCNC(=O)CCNC(=O)(C(C)(C)COP(=O)(O)OP(=O)(O)OC1(((O1)N2C=NC3=C(N=CN=C32)N)O)OP(=O)(O)O)O)O
Properties
Chemical formula	C₂₆H₄₄N₇O₁₈P₃S
Molar mass	867.649946
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references

Chemical compound

β-Hydroxy β-methylbutyryl-coenzyme A (HMB-CoA), also known as 3-hydroxyisovaleryl-CoA, is a metabolite of L-leucine that is produced in the human body. Its immediate precursors are β-hydroxy β-methylbutyric acid (HMB) and β-methylcrotonoyl-CoA (MC-CoA). It can be metabolized into HMB, MC-CoA, and HMG-CoA in humans.

Metabolic pathway

Leucine metabolism in humans

L-Leucine Branched-chain amino
acid aminotransferase α-Ketoglutarate Glutamate Glutamate Alanine Pyruvate Muscle: α-Ketoisocaproate (α-KIC) Liver: α-Ketoisocaproate (α-KIC) Branched-chain α-ketoacid
dehydrogenase (mitochondria) KIC-dioxygenase
(cytosol) Isovaleryl-CoA β-Hydroxy
β-methylbutyrate
(HMB) Excreted
in urine
(10–40%)

HMB-CoA β-Hydroxy β-methylglutaryl-CoA
(HMG-CoA) β-Methylcrotonyl-CoA
(MC-CoA) β-Methylglutaconyl-CoA
(MG-CoA) CO₂ CO₂ O₂ CO₂ H₂O CO₂ H₂O (liver)
HMG-CoA
lyase Enoyl-CoA hydratase Isovaleryl-CoA
dehydrogenase MC-CoA
carboxylase MG-CoA
hydratase HMG-CoA
reductase HMG-CoA
synthase β-Hydroxybutyrate
dehydrogenase Mevalonate
pathway Thiolase Unknown
enzyme β-Hydroxybutyrate Acetoacetyl-CoA Acetyl-CoA Acetoacetate Mevalonate Cholesterol

Human metabolic pathway for HMB and isovaleryl-CoA relative to L-leucine. Of the two major pathways, L-leucine is mostly metabolized into isovaleryl-CoA, while only about 5% is metabolized into HMB.

Notes

This reaction is catalyzed by an unknown thioesterase enzyme.

References

^ Wilson JM, Fitschen PJ, Campbell B, Wilson GJ, Zanchi N, Taylor L, Wilborn C, Kalman DS, Stout JR, Hoffman JR, Ziegenfuss TN, Lopez HL, Kreider RB, Smith-Ryan AE, Antonio J (February 2013). "International Society of Sports Nutrition Position Stand: beta-hydroxy-beta-methylbutyrate (HMB)". Journal of the International Society of Sports Nutrition. 10 (1): 6. doi:10.1186/1550-2783-10-6. PMC 3568064. PMID 23374455.
^ Kohlmeier M (May 2015). "Leucine". Nutrient Metabolism: Structures, Functions, and Genes (2nd ed.). Academic Press. pp. 385–388. ISBN 978-0-12-387784-0. Retrieved 6 June 2016. Energy fuel: Eventually, most Leu is broken down, providing about 6.0kcal/g. About 60% of ingested Leu is oxidized within a few hours ... Ketogenesis: A significant proportion (40% of an ingested dose) is converted into acetyl-CoA and thereby contributes to the synthesis of ketones, steroids, fatty acids, and other compounds
Figure 8.57: Metabolism of L-leucine
"KEGG Reaction: R10759". Kyoto Encyclopedia of Genes and Genomes. Kanehisa Laboratories. Retrieved 24 June 2016.
Mock DM, Stratton SL, Horvath TD, Bogusiewicz A, Matthews NI, Henrich CL, Dawson AM, Spencer HJ, Owen SN, Boysen G, Moran JH (November 2011). "Urinary excretion of 3-hydroxyisovaleric acid and 3-hydroxyisovaleryl carnitine increases in response to a leucine challenge in marginally biotin-deficient humans". primary source. The Journal of Nutrition. 141 (11): 1925–1930. doi:10.3945/jn.111.146126. PMC 3192457. PMID 21918059. Metabolic impairment diverts methylcrotonyl CoA to 3-hydroxyisovaleryl CoA in a reaction catalyzed by enoyl-CoA hydratase (22, 23). 3-Hydroxyisovaleryl CoA accumulation can inhibit cellular respiration either directly or via effects on the ratios of acyl CoA:free CoA if further metabolism and detoxification of 3-hydroxyisovaleryl CoA does not occur (22). The transfer to carnitine by 4 carnitine acyl-CoA transferases distributed in subcellular compartments likely serves as an important reservoir for acyl moieties (39–41). 3-Hydroxyisovaleryl CoA is likely detoxified by carnitine acetyltransferase producing 3HIA-carnitine, which is transported across the inner mitochondrial membrane (and hence effectively out of the mitochondria) via carnitine-acylcarnitine translocase (39). 3HIA-carnitine is thought to be either directly deacylated by a hydrolase to 3HIA or to undergo a second CoA exchange to again form 3-hydroxyisovaleryl CoA followed by release of 3HIA and free CoA by a thioesterase.
^ Zanchi NE, Gerlinger-Romero F, Guimarães-Ferreira L, de Siqueira Filho MA, Felitti V, Lira FS, Seelaender M, Lancha AH (April 2011). "HMB supplementation: clinical and athletic performance-related effects and mechanisms of action". Amino Acids. 40 (4): 1015–1025. doi:10.1007/s00726-010-0678-0. PMID 20607321. S2CID 11120110. HMB is a metabolite of the amino acid leucine (Van Koverin and Nissen 1992), an essential amino acid. The first step in HMB metabolism is the reversible transamination of leucine to that occurs mainly extrahepatically (Block and Buse 1990). Following this enzymatic reaction, may follow one of two pathways. In the first, HMB is produced from by the cytosolic enzyme KIC dioxygenase (Sabourin and Bieber 1983). The cytosolic dioxygenase has been characterized extensively and differs from the mitochondrial form in that the dioxygenase enzyme is a cytosolic enzyme, whereas the dehydrogenase enzyme is found exclusively in the mitochondrion (Sabourin and Bieber 1981, 1983). Importantly, this route of HMB formation is direct and completely dependent of liver KIC dioxygenase. Following this pathway, HMB in the cytosol is first converted to cytosolic β-hydroxy-β-methylglutaryl-CoA (HMG-CoA), which can then be directed for cholesterol synthesis (Rudney 1957) (Fig. 1). In fact, numerous biochemical studies have shown that HMB is a precursor of cholesterol (Zabin and Bloch 1951; Nissen et al. 2000).

Amino acid metabolism metabolic intermediates

K→acetyl-CoA

lysine→	Saccharopine Allysine α-Aminoadipic acid 2-Oxoadipic acid Glutaryl-CoA Glutaconyl-CoA Crotonyl-CoA β-Hydroxybutyryl-CoA
leucine→	β-Hydroxy β-methylbutyric acid β-Hydroxy β-methylbutyryl-CoA Isovaleryl-CoA α-Ketoisocaproic acid β-Ketoisocaproic acid β-Ketoisocaproyl-CoA β-Leucine β-Methylcrotonyl-CoA β-Methylglutaconyl-CoA β-Hydroxy β-methylglutaryl-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

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 α-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

Cholesterol and steroid metabolic intermediates

Mevalonate pathway

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 Steroid hormones

Nonhuman

To Sitosterol	Cycloartenol Cycloeucalenol Obtusifoliol 4α-methylfecosterol Isofucosterol 24-Methylenelophenol Sitosterol More Phytosterols see here instead.
To Ergocalciferol	Fecosterol Episterol Ergostatrienol Ergostatetraenol Ergosterol Ergocalciferol

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