Amino Acids

General Literature

Introduction In Living Systems.

Amino acids play many important roles in living systems. They are used as building blocks for peptides which in turn serve to provide structure, transport or catalysis in the organisms. Furthermore amino acids act as metabolic intermediates and substrates. They may even serve as information carriers in the form of an excitotoxic substance or as an enzyme effector. Finally amino acids contribute to system parameters such as pH, ionic strength, electric-, osmotic- and redoxpotential.

Introduction In Biochemical Studies

The identity and amount of an amino acid may be of interest per se, as a parameter of a dynamic system, or as a building block of a peptide. Amino acids may be targets as in group-specific modification to study enzyme function, or in the preparation of heavy-atom derivatives to determine the structure of a crystalline protein.

As Tools in Biochemical Work

Amino acids can be used as tools in biochemistry for a variety of purposes. These include components of buffers and culture media, as substrates in enzymology, as protectors or stabilizers and in electrophoretic techniques. As the ampholytic properties of the amino acids may play a significant role in their applications, data on pK and pl values have been tabulated.

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Values

pK and pl Values of Amino Acids in Aqueous Solutions at 25°C

Amino acid	Symbols			pK1	pK2	pK3	pK4	pl	Ref.
Alanine	A	Ala	2.35		9.87			6.11	[1]
AIanine			3.55		10.24			6.90	[2]*
Arginine	R	Arg	2.01		9.04	12.48		10.76	[1]
Asparagine	N	Asn	2.14		8.72			5.43	[2]*
Aspartic acid	D	Asp	2.10		3.86	9.82		2.98	[1]
Cysteine	C	Cys	1.92		8.37	10.70		5.15	[2]*
Cystine			1.04		2.05	8.00	10.25	5.02	[1]
Glutamic acid	E	Glu	2.10		4.07	9.47		3.08	[1]
Glutamine	Q	Gln	2.17		9.13			5 65	[2]*
Glycine	G	Gly	2.35		9.78			6.06	[1]
Histidine	H	His	1.77		6.10	9.18		7.64	[1]
Isoleucine	I	lle	2.32		9.76			6.04	[2]*
Leucine	L	Leu	2.33		9.74			6.04	[2]*
Lysine	K	Lys	2.18		8.95	10.53		9.47	[1]
Methionine	M	Met	2.13		9.28			5.71	[2]*
Ornithine		Orn	1.71		8.69	10.76		9.73	[2]*
Phenylalanine	F	Phe	2.20		9.31			5.76	[2]*
Proline	P	Pro	2.00		10.60			6 30	[1]
Sarcosine		Sar	2.12		10.2			6.16	[2]*
Serine	S	Ser	2.19		9.21			5 70	[2]*
Threonine	T	Thr	2.09		9.10			5.60	[2]*
Tryptophan	W	Trp	2.38		9.39			5.88	[1]
Tyrosine	Y	Tyr	2.20		9.11	10.07		5.63	[1]
Valine	V	Val	2.29		9.74			6.02	[2]*

*: in ref. 2, only the pK data are given we have calculated the pl value as: pl=1/2(pK_i+pK_i+1),
with i = 2 for ornithine
and i = 1 in all other cases.

References

1. CRC Handbook of Chemistry and Physics, 66th ed., CRC Press, Boca Raton, Florida (1985).
2. R.M.C. Dawson, D.C. Elliott, W.H. Elliott, K.M. Jones, Data for Biochemical Research 3rd ed., Clarendon Press Oxford (1986).

General Literature

J.P Greenstein, M.Winitz, Chemistry of the Amino Acids, 3 vols., Wiley, New York (1961)

Chemistry and Biochemistry of the Amino Acids, ed. G.C. Barrett, Chapman and Hall, London (1984). Focus on advance since the treatise by Greenstein & Winitz.

A. Meister, Biochemistry of the Amino Acids 2nd ed., 2 vols., Academic Press, New York (1965).

Methods in Enzymology, vol. XVII: Metabolism of Amino acids (1971).

b-alanine
F.V. De Feudis, R. Martin del Rio, Is b-alanine an inhibitory neurotransmitter?
Gen. Pharmacol. 8, 177 (1977).

The biochemistry of aspartic acid and asparagine
Methods in Enzymology, vol.113, Section IV: Aspartate and Asparagine (1985).

The biochemistry of glutamic acid
Methods in Enzymology, vol.113, Section l: Glutamate (1985).

The biochemistry of the sulfur containing amino acids
A.J.L. Cooper, Biochemistry of the sulfur containing amino acids, Ann. Rev. Biochem. 52, 187 (1983).

Nomenclature and symbolism
W.E. Cohn, Nomenclature and Symbolism of a-Amino acids, Methods Enzymol. 106, 3 (1984). Includes a lot of modified forms of "the Common 20" alpha-amino acids that have been found in proteins.

Physiochemical data
CRC Handbook of Chemistry and Physics, 66th ed., CRC Press, Boca Raton, Florida (1985).
R.M.C. Dawson, D.C. Elliott, W.H. Elliott,
K.M.Jones, Data for Biochemical Research,
3rd ed., Clarendon Press, Oxford (1986).
With useful remarks on stability.

Amino acids in microbiology
CRC Handbook of Microbiology, vol.3: Microbial Products, eds. A.l. Laskin, H.A. Lechevalier, CRC Press, Cleveland, Ohio (1974).
CRC Handbook of Microbiology, vol.4: Microbial Metabolism, Genetics and Immunology, eds. A.l. Laskin, H.A. Lechevalier, CRC Press, Cleveland, Ohio (1974). Contains information on the grovvth requirements of various microorganisms.

Amino acids in neurology
Neuromethods, vol.3: Amino acids, eds. A.A.Boulton, G.B.Baker, J.D.Wood Humana Press, Clifton, New Jersey (1985).

Amino acids as spacers in isotachophoresis
N.Y Nguyen, A. Chrambach, Amino acid spacing in isotachophoresis on polyacrylamide gel: a critical evaluation, Anal. Biochem. 94, 202 (1979).

Amino acid analysis
Methods in Enzymology, vol.91, Section l: Amino Acid Analysis and related Procedures (1983).
Methods in Enzymology, vol.94: Polyamines, Section l: Analytical Methods for Amines (1983).
.S. Inglis, Single Hydrolysis Method for all Amino Acids, Including Cysteine and Tryptophan, Methods Enzymol. 91, 26 (1983).

A review of the literature publishod since 1968, giving the most recent volume
Amino Acids, Peptides and Proteins, vol.16, a review of the literature published during 1983, a Specialist Periodical Report, The Royal Society of Chemistry, London (1985).