J. C. Dobrowolsk et al.
144
Table A3 Roles of free amino acids in organisms
AA
Role
Alanine
glucose—alanine cycle; ammonia carrier [A24]
Arginine
healing of injuries and damaged tissue [A66, A67]
Increases growth hormone secretion and thereby influences immune function
[A68]
Supplementation or intravenous administration of arginine is beneficial in
improving reproductive, cardiovascular, pulmonary, renal, gastrointestinal,
liver and immune functions, as well as enhancing insulin sensitivity [A69]
Asparagine
Presence of free asparagine in blood is an essential factor for the growth of
leukaemic blasts [A70–A73]
In plants: nitrogen storage and nitrogen transport compound [A74]
Aspartic acid
Neurotransmitter: stimulates NmdA receptors [A75]
malate-aspartate shuttle [A76]
Cysteine
Precursor to the antioxidant glutathione: playing a critical role in cellular
defenses against oxidative stress, free radicals, detoxifyication. [A77, A78]
Involved in cobalt ion complexation in plant cells [A79]
glutamine
Nontoxic transporter of ammonia in the blood circulation [A80]
Regulation of acid-base balance in the kidney by producing ammonium
[A80]
Anabolic action after oral and intravenous administration; reducing of healing times after operations [A81]
glutamic acid
An excitatory neurotransmitter (while its metabolite gABA is a inhibitory
one) [A27]
disposal of excess or waste nitrogen [A27]
glycine
Inhibitory neurotransmitter in the central nervous system [A82]
there is some evidence of glycine improving sleep quality [A83]
histidine
In plants the free L-histidine content increases tolerance to Ni and also elevates tolerance to Co and Zn [A84, A85]
Isoleucine
Shuttle molecule for the exchange of nitrogen in the glutamate/glutamine
cycle. [A86] disorders in its utilization usually characterized by neuropathological symptoms [A86]
In plants: stress tolerance [A10]
Leucine
Regulates glucose-alanine cycle [A24]
l-leucine supplementation during feeding improves muscle protein synthesis
in the elderly independently of an overall increase of other amino acids.
[A77]
Effective at attenuating muscle atrophy during exercise stress, and in models
of cancer, congestive heart failure, sepsis, and hIv. [A78]
Shuttle molecule for the exchange of nitrogen in the glutamate/glutamine
cycle. [A86] disorders in its utilization usually characterized by neuropathological symptoms [A86]
In plants: stress tolerance [A10]
Lysine
Inhibits normal replication of herpes simplex virus, accelerates recovery from
the infection and suppressing recurrence [A89, A90]
Serotonin antagonist [A91]
In plants: related to seed, root elongation and floral development as well as
responce to abiotic stress [A39]
methionine
In the synthesis of eukaryotic proteins methionine is the initiating amino acid
usually removed after the protein is synthesized [A92]
144
Table A3 Roles of free amino acids in organisms
AA
Role
Alanine
glucose—alanine cycle; ammonia carrier [A24]
Arginine
healing of injuries and damaged tissue [A66, A67]
Increases growth hormone secretion and thereby influences immune function
[A68]
Supplementation or intravenous administration of arginine is beneficial in
improving reproductive, cardiovascular, pulmonary, renal, gastrointestinal,
liver and immune functions, as well as enhancing insulin sensitivity [A69]
Asparagine
Presence of free asparagine in blood is an essential factor for the growth of
leukaemic blasts [A70–A73]
In plants: nitrogen storage and nitrogen transport compound [A74]
Aspartic acid
Neurotransmitter: stimulates NmdA receptors [A75]
malate-aspartate shuttle [A76]
Cysteine
Precursor to the antioxidant glutathione: playing a critical role in cellular
defenses against oxidative stress, free radicals, detoxifyication. [A77, A78]
Involved in cobalt ion complexation in plant cells [A79]
glutamine
Nontoxic transporter of ammonia in the blood circulation [A80]
Regulation of acid-base balance in the kidney by producing ammonium
[A80]
Anabolic action after oral and intravenous administration; reducing of healing times after operations [A81]
glutamic acid
An excitatory neurotransmitter (while its metabolite gABA is a inhibitory
one) [A27]
disposal of excess or waste nitrogen [A27]
glycine
Inhibitory neurotransmitter in the central nervous system [A82]
there is some evidence of glycine improving sleep quality [A83]
histidine
In plants the free L-histidine content increases tolerance to Ni and also elevates tolerance to Co and Zn [A84, A85]
Isoleucine
Shuttle molecule for the exchange of nitrogen in the glutamate/glutamine
cycle. [A86] disorders in its utilization usually characterized by neuropathological symptoms [A86]
In plants: stress tolerance [A10]
Leucine
Regulates glucose-alanine cycle [A24]
l-leucine supplementation during feeding improves muscle protein synthesis
in the elderly independently of an overall increase of other amino acids.
[A77]
Effective at attenuating muscle atrophy during exercise stress, and in models
of cancer, congestive heart failure, sepsis, and hIv. [A78]
Shuttle molecule for the exchange of nitrogen in the glutamate/glutamine
cycle. [A86] disorders in its utilization usually characterized by neuropathological symptoms [A86]
In plants: stress tolerance [A10]
Lysine
Inhibits normal replication of herpes simplex virus, accelerates recovery from
the infection and suppressing recurrence [A89, A90]
Serotonin antagonist [A91]
In plants: related to seed, root elongation and floral development as well as
responce to abiotic stress [A39]
methionine
In the synthesis of eukaryotic proteins methionine is the initiating amino acid
usually removed after the protein is synthesized [A92]