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Chapter 14 · Building Blocks of Life - Amino Acids
14
Isoleucine (Ile) was isolated from molasses in
1903 by Felix Ehrlich. This essential amino acid
is also found in meat and cereal proteins and up
to 7% in milk and egg proteins. It is important
for the human diet: A lack of isoleucine can lead
to weight loss.
Leucine (Leu, Greek: leukos, white) was
extracted from wool by Henry Braconnot in
1820. Leucine is also essential and is found in
most proteins in amounts of up to 10%. Leucine
is of great importance for the development and
maintenance of muscle tissue. It is therefore a
component of medical infusion solutions and is
used in weight training to build up muscles.
Lysine (Lys) is a basic essential amino acid
first isolated in 1889 from casein, the protein
component of milk. It is also found in meat and
egg proteins. Crab and fish proteins have the
highest content of lysine with 10–11%. Since
lysine is responsible for length growth in humans,
its deficiency leads to a small stature. Lysine
is added to the animal feed for pigs, and thus
the nutritional value of the feed is significantly
increased. l-lysine production is 850,000 t a −1 .
Methionine (Met) got its name after the
methylthio group typical for the molecule. It was
extracted from casein in 1922 by the American
John Howard Müller. In metabolism, methionine
is an important supplier for the methyl group, e.g.
in the biosynthesis of nucleic acids or adrenalin.
Vegetable proteins contain up to 2% methionine,
while animal proteins contain up to 4% methionine. This amino acid is very sensitive to oxygen and heat and is responsible for body and hair
growth. Similar to lysine, methionine is used in
animal nutrition, mainly as an additive to poultry feed. Methionine is also effective as a racemate
(i.e. mixture of the d- and l-configured amino
acids). 1 kg (dl)-methionine can replace approx.
50 kg fish meal in poultry feed. Due to the large
demand for methionine, it is chemically synthesized in quantities of >400,000 t a −1 . A process that
is still successfully practiced today was developed
by Degussa AG in 1946. The successor to Degussa
AG, Evonik Industries, has commissioned several large-scale plants worldwide using this process. . Figure 14.6 shows the multistage synthesis
pathway of this process. In total, (dl)-methionine
is produced from methyl mercaptan, acrolein,
hydrocyanic acid and water, i.e. from industrially
easily accessible starting materials.
mainly for the synthesis of the sweetener aspartame (7 Sect. 14.2).
Cysteine (Cys, pronounced: cyste-in) contains a mercapto group in the side chain. It was
named after the bladder (Greek: kystis) because
it was first isolated from bladder stones in 1810.
It occurs in quantities of up to 9% in keratins,
which serve as skeletal substances in animal
organisms, e.g. in hair, feathers, toenails, hooves
or dandruff. Cysteine is also found in plants, e.g.
in fungi, peas, maize and grapes. Cysteine is not
an essential amino acid because adults produce it
in their liver. It is of great importance in protein
chemistry because two cysteine molecules can be
linked by a disulfide bridge.
Glutamine (Gln) was extracted from sugar
beet juice in 1883, but is also found in potatoes
and numerous other plants. Like asparagine, it
contains an amide group in its side chain. Glutamine is an important nitrogen reservoir for
animals, fungi and bacteria.
Glutamic acid (Glu) contains a second carboxyl group instead of the amide group of glutamine. The name derives from the Latin word
for glue (glutinum) because it was first isolated
from wheat gluten. It occurs in large amounts
in many proteins, e.g. wheat protein (31%), milk
protein (22%) and soy protein (19%). Glutamic
acid itself and its monosodium salt, sodium glutamate, are added to numerous foods - especially
in Asia - to enhance taste. Since large quantities
are required for this, l-glutamic acid is produced
industrially in the amount of 1.6 million tons per
year through the fermentation of d-glucose.
Glycine (Gly), the only non-chiral amino
acid, was isolated from gelatine, i.e. collagen hydrolyzate, in 1820 by Henry Braconnot (. Fig. 9.2). This simplest amino acid
(. Fig. 14.1) got its name after its sweet taste
(Greek: glycos, sweet). Glycine is present to a
large amount (25–30%) in numerous structural proteins. The industrial importance of glycine is relatively low; its annual production is
22,000 t a −1 .
Histidine (His) belongs to the group of heterocyclic amino acids since it has an imidazole residue. Histidine is not essential for adults, but it is
for toddlers. Histidine is necessary for the formation of the blood pigment: blood proteins contain up to 6% of histidine. Many other proteins
contain up to 3% of histidine.
Chapter 14 · Building Blocks of Life - Amino Acids
14
Isoleucine (Ile) was isolated from molasses in
1903 by Felix Ehrlich. This essential amino acid
is also found in meat and cereal proteins and up
to 7% in milk and egg proteins. It is important
for the human diet: A lack of isoleucine can lead
to weight loss.
Leucine (Leu, Greek: leukos, white) was
extracted from wool by Henry Braconnot in
1820. Leucine is also essential and is found in
most proteins in amounts of up to 10%. Leucine
is of great importance for the development and
maintenance of muscle tissue. It is therefore a
component of medical infusion solutions and is
used in weight training to build up muscles.
Lysine (Lys) is a basic essential amino acid
first isolated in 1889 from casein, the protein
component of milk. It is also found in meat and
egg proteins. Crab and fish proteins have the
highest content of lysine with 10–11%. Since
lysine is responsible for length growth in humans,
its deficiency leads to a small stature. Lysine
is added to the animal feed for pigs, and thus
the nutritional value of the feed is significantly
increased. l-lysine production is 850,000 t a −1 .
Methionine (Met) got its name after the
methylthio group typical for the molecule. It was
extracted from casein in 1922 by the American
John Howard Müller. In metabolism, methionine
is an important supplier for the methyl group, e.g.
in the biosynthesis of nucleic acids or adrenalin.
Vegetable proteins contain up to 2% methionine,
while animal proteins contain up to 4% methionine. This amino acid is very sensitive to oxygen and heat and is responsible for body and hair
growth. Similar to lysine, methionine is used in
animal nutrition, mainly as an additive to poultry feed. Methionine is also effective as a racemate
(i.e. mixture of the d- and l-configured amino
acids). 1 kg (dl)-methionine can replace approx.
50 kg fish meal in poultry feed. Due to the large
demand for methionine, it is chemically synthesized in quantities of >400,000 t a −1 . A process that
is still successfully practiced today was developed
by Degussa AG in 1946. The successor to Degussa
AG, Evonik Industries, has commissioned several large-scale plants worldwide using this process. . Figure 14.6 shows the multistage synthesis
pathway of this process. In total, (dl)-methionine
is produced from methyl mercaptan, acrolein,
hydrocyanic acid and water, i.e. from industrially
easily accessible starting materials.
mainly for the synthesis of the sweetener aspartame (7 Sect. 14.2).
Cysteine (Cys, pronounced: cyste-in) contains a mercapto group in the side chain. It was
named after the bladder (Greek: kystis) because
it was first isolated from bladder stones in 1810.
It occurs in quantities of up to 9% in keratins,
which serve as skeletal substances in animal
organisms, e.g. in hair, feathers, toenails, hooves
or dandruff. Cysteine is also found in plants, e.g.
in fungi, peas, maize and grapes. Cysteine is not
an essential amino acid because adults produce it
in their liver. It is of great importance in protein
chemistry because two cysteine molecules can be
linked by a disulfide bridge.
Glutamine (Gln) was extracted from sugar
beet juice in 1883, but is also found in potatoes
and numerous other plants. Like asparagine, it
contains an amide group in its side chain. Glutamine is an important nitrogen reservoir for
animals, fungi and bacteria.
Glutamic acid (Glu) contains a second carboxyl group instead of the amide group of glutamine. The name derives from the Latin word
for glue (glutinum) because it was first isolated
from wheat gluten. It occurs in large amounts
in many proteins, e.g. wheat protein (31%), milk
protein (22%) and soy protein (19%). Glutamic
acid itself and its monosodium salt, sodium glutamate, are added to numerous foods - especially
in Asia - to enhance taste. Since large quantities
are required for this, l-glutamic acid is produced
industrially in the amount of 1.6 million tons per
year through the fermentation of d-glucose.
Glycine (Gly), the only non-chiral amino
acid, was isolated from gelatine, i.e. collagen hydrolyzate, in 1820 by Henry Braconnot (. Fig. 9.2). This simplest amino acid
(. Fig. 14.1) got its name after its sweet taste
(Greek: glycos, sweet). Glycine is present to a
large amount (25–30%) in numerous structural proteins. The industrial importance of glycine is relatively low; its annual production is
22,000 t a −1 .
Histidine (His) belongs to the group of heterocyclic amino acids since it has an imidazole residue. Histidine is not essential for adults, but it is
for toddlers. Histidine is necessary for the formation of the blood pigment: blood proteins contain up to 6% of histidine. Many other proteins
contain up to 3% of histidine.