AA Comp - Acid Hydrolysis

BL/CH 401 Lecture #5 - Protein Primary Structure

2. Amino Acid Composition

Amino Acid analysis yields a protein's Amino Acid Composition, in other words the amounts of each amino acid in the protein. All proteins have unique amino acid compositions.

Amino acid compositions of a few proteins (see list proteins below table)
Values for Amino Acids are in Number of Residues per Molecule of Protein

Amino Acid \ Protein	A	B	C	D	E	F	G	H	I
Nonpolar
Ala (A)	12	6	9	1	3	27	15	12	27
Val (V)	13	3	7	1	4	13	18	6	14
Leu (L)	15	6	8	2	6	18	18	8	38
Ile (I)	9	8	4	0	1	0	0	6	12
Pro (P)	11	4	4	0	1	7	7	2	2
Met (M)	1	3	0	1	0	2	1	2	2
Phe (F)	10	3	2	2	3	7	8	3	4
Trp (W)	2	1	1	1	0	1	2	6	0
Polar, Uncharged
Gly (G)	13	13	6	1	4	7	13	12	14
Ser (S)	28	2	7	4	3	11	5	10	27
Thr (T)	19	7	8	3	1	9	7	7	15
Tyr (Y)	9	5	4	2	4	3	3	3	8
Cys (C)	5	2	5	0	6	1	2	8	15
Asn (N)	10	5	2	1	0	4	6	13	17
Gln (Q)	16	2	4	3	0	1	3	3	25
Polar, Negative Charge
Asp (D)	10	3	11	3	3	8	7	8	17
Glu (E)	10	8	9	0	7	4	8	2	26
Polar, Positive Charge
Lys (K)	13	18	4	1	1	11	11	6	18
Arg (R)	6	2	1	2	9	3	3	11	11
His (H)	2	3	1	1	2	10	9	1	2
Total Residues	214	104	97	29	54	141	146	129	312

List of Proteins Shown in Amino Acid Composition Table:

A. Antibody - Human Bence-Jones Kappa (antibody light chain)
B. Human Cytochrome c (electron transport protein)
C. Spinach Ferredoxin (electron transport protein)
D. Pig Glucagon (protein hormone)
E. Bovine Insulin (protein hormone)
F. Human/Gorilla Hemoglobin alpha chain (oxygen transport protein)
G. Human/Gorilla Hemoglobin beta chain (oxygen transport protein)
H. Chicken Lysozyme (enzyme)
I. Sheep Wool (structural protein)

Free amino acids are obtained from proteins by strong acid hydrolysis:

{*Figure 7*}

3 of the standard 20 AAs are lost during Acid Hydrolysis treatment:

{*Figure 8*}

The amide AAs, Asn & Gln, are converted to their acids, Asp & Glu.

Trp is simply unstable under acid hydrolysis conditions and is destroyed.

Despite the loss of 3 AAs, 6 N HCl and 110 C are the conditions of choice for protein hydrolysis.

The amounts of the remaining 17 AA are determined by

Amino Acid Analysis

with an Amino Acid Analyzer (an analytical instrument).