Isoleucine

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Structural formula
L-Isoleucine - L-Isoleucine.svg
L -Isoleucine For
structures of other isomers see stereoisomerism
General
Surname Isoleucine
other names
Molecular formula C 6 H 13 NO 2
Brief description

colorless solid with a faint odor

External identifiers / databases
CAS number 73-32-5 ( L -isoleucine)
EC number 200-798-2
ECHA InfoCard 100,000,726
PubChem 6306
ChemSpider 6067
DrugBank DB00167
Wikidata Q484940
Drug information
ATC code

V06 

properties
Molar mass 131.18 g mol −1
Physical state

firmly

Melting point

284 ° C (decomposition, L -isoleucine)

pK s value
  • pK COOH : 2.32 (25 ° C, L -isoleucine)
  • pK NH 2 : 9.76 (25 ° C, L- isoleucine)
solubility

soluble in water (40 g l −1 at 20 ° C, L -isoleucine)

safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Isoleucine , abbreviated Ile or I , is in its natural L -form an essential proteinogenic α - amino acid .

Since isoleucine can be derived from aspartic acid , it belongs to the aspartate group . It belongs together with its structural isomers leucine , norleucine and tert -leucine for substance group of leucine .

history

In 1901, Emil Fischer , who later won the Nobel Prize , suggested that the leucine fraction he isolated contained, in addition to leucine, an "amino acid of the same composition but with a stronger rotation". In fact, in 1903 the German chemist Felix Ehrlich was able to isolate a compound isomeric to leucine from the molasses of beet sugar , called isoleucine. Felix Ehrlich recognized the constitution in 1907 through further investigation.

Occurrence

Isoleucine is a peptide- bound component of animal and vegetable proteins . The following examples each relate to 100 g of the foodstuff; the percentage of isoleucine in the total protein is also given.

Food protein Isoleucine proportion of
beef 21.26 g 0967 mg 4.5%
Chicken breast fillet 23.09 g 1219 mg 5.3%
salmon 20.42 g 0968 mg 4.7%
Chicken egg 12.58 g 0672 mg 5.3%
Cow's milk, 3.7% fat 03.28 g 0198 mg 6.0%
Walnuts 15.23 g 0625 mg 4.1%
Wholemeal wheat flour 13.70 g 0508 mg 3.7%
Wholemeal corn flour 06.93 g 0248 mg 3.6%
Rice, unpeeled 07.94 g 0336 mg 4.2%
Peas, dried 24.55 g 1014 mg 4.1%

All of these foods contain almost exclusively chemically bound L -isoleucine as a protein component, but no free L -isoleucine in the raw state .

Stereoisomerism

Isoleucine has two stereocenters, so there are four stereoisomers ; In our environment, however, only L -isoleucine plays a role as a proteinogenic amino acid and is physiologically important. When "isoleucine" is spoken of without any additional name ( descriptor ), L- isoleucine is generally meant.

D -isoleucine is the enantiomer of natural L -isoleucine. L - allo -isoleucine and its enantiomer D - allo -isoleucine are diastereomers of L -isoleucine.

Isomers of isoleucine
Surname L -isoleucine D -isoleucine L - allo -isoleucine D - allo -isoleucine
other names (2 S , 3 S ) -2-amino-3-methylpentanoic acid

( S ) -isoleucine

(2 R , 3 R ) -2-amino-3-methylpentanoic acid

(2 R , 3 R ) -2-amino-3-methylvaleric acid
( R ) -Isoleucine

(2 S , 3 R ) -2-amino-3-methylpentanoic acid (2 R , 3 S ) -2-amino-3-methylpentanoic acid
Structural formula L-Isoleucine - L-Isoleucine.svg D-isoleucine.svg L-alloisoleucine.svg D-alloisoleucine.svg
CAS number 73-32-5 319-78-8 1509-34-8 1509-35-9
443-79-8 (unspec.)
EC number 200-798-2 206-269-2 216-142-3 216-143-9
207-139-8 (unspec.)
ECHA info card 100,000,726 100.005.701 100.014.675 100.014.676
100.006.492 (unspec.)
PubChem 6306 76551 99288 94206
791 (unspec.)
Wikidata Q484940 Q27103290 Q27092902 Q27109362
Q27117434 (unspec.)
Melting point Decomposition: 284 ° C

properties

Isoleucine is present at the isoelectric point (a certain pH value ) as a zwitterion (inner salt), with the proton of the carboxy group (-COOH) dissociating and the amino group (-NH 2 ) protonating.

Biochemical significance

On the one hand, isoleucine is required as a building block for protein synthesis. On the other hand, it can also be used to generate energy in muscle cells . This plays a role in protein-rich food or during longer exertion and in phases of hunger when the body draws on its own reserves. The breakdown of isoleucine provides acetyl-CoA and propionyl-CoA .

Estimates of the daily requirement for healthy adults range, depending on the method used, from 7.5 to 28 mg isoleucine per kilogram of body weight. In the human organism, isoleucine occurs almost exclusively in a bound state. The concentration of free isoleucine in the blood is around 7 mg / l; 10 to 15 mg are excreted in the urine every day.

Extraction

The main extraction methods are fermentation processes in which glucose-containing solutions with the addition of L - threonine are converted by microorganisms producing L- isoleucine. In contrast, a mixture of the natural amino acids L- leucine and L- isoleucine is obtained by hydrolysis of proteins and subsequent separation operations of the hydrolysates . These constitutional isomers can then be z. B. separate by an enzymatic process.

use

As a component of amino acid infusion solutions for parenteral nutrition, L -Isoleucine, along with other amino acids, is widely used in human medicine. An orally administered “chemically defined diet” containing L- isoleucine was developed for patients with impaired digestion . In this diet, the amino acids are the source of nitrogen; all vital nutrients are in a chemically precisely defined form.

Web links

Wikibooks: Biochemistry and Pathobiochemistry: Valine, Leucine and Isoleucine Metabolism  - Learning and Teaching Materials
Wiktionary: Isoleucine  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c d e f Entry on L-isoleucine in the GESTIS substance database of the IFA , accessed on February 5, 2018(JavaScript required) .
  2. ^ A b Hans Beyer, Wolfgang Walter: Textbook of Organic Chemistry . Hirzel Verlag, Stuttgart 1991, ISBN 3-7776-0485-2 , p. 823.
  3. ↑ S. Hansen: The discovery of proteinogenic amino acids from 1805 in Paris to 1935 in Illinois . ( Memento of the original from June 15, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF) Berlin 2015. @1@ 2Template: Webachiv / IABot / www.arginium.de
  4. ↑ F. Ehrlich: About the natural isomer of leucine . In: Ber Deutsche Chem Ges , Volume 37, pp. 1809-1840 (1904), doi: 10.1002 / cber.19040370295 .
  5. ↑ F. Ehrlich: About the natural isomer of leucine. Constitution and synthesis of isoleucine . In: Ber Deutsche Chem Ges , Volume 40 (2), pp. 2538-2562 (1907), doi: 10.1002 / cber.190704002181 .
  6. ↑ nutrient database of the US Department of Agriculture , 21st edition.
  7. ↑ Bernd Hoppe, Jürgen Martens: Amino acids - production and extraction . In: Chemistry in our time , 1984, 18, pp. 73-86.
  8. ↑ JM Berg, JL Tymoczko, L. Stryer: Biochemistry. 6th edition. Spectrum Academic Publishing House, Elsevier, Munich 2007; Pp. 735, 746; ISBN 978-3-8274-1800-5 .
  9. ↑ AV Kurpad, MM Regan, T. Raj, JV Gnanou: Branched-chain amino acid requirements in healthy adult human subjects . In: J. Nutr. , 2006, 136 (1 Suppl), pp. 256S-263S, PMID 16365094 .
  10. ^ Roche Lexicon Medicine. 5th edition. Urban & Fischer Verlag, Elsevier, Munich 2003, ISBN 978-3-437-15150-7 .
  11. ↑ a b Yoshiharu Izumi, Ichiro Chibata and Tamio Itoh: Production and Use of Amino Acids . In: Angewandte Chemie , 1987, 90, pp. 187-194. Angewandte Chemie International Edition in English , 1978, 17, pp. 176-183.
  12. ↑ Hitoshi Enei, Kenzo Yokozeki, Kunihiko Akashi: Recent Progress in Microbial Production of Amino Acids . Gordon & Breach Science Publishers, 1989, ISBN 978-2-88124-324-0 , p. 61.
  13. ↑ Jürgen Martens , Horst Weigel: Enzymatic Separation of L -Leucine and L -Isoleucine . In: Liebigs Annalen der Chemie , 1983, pp. 2052-2054.