Enzyme Reagents

Human Albumin

Gene ID: ALB
CAS#: 70024-90-7

Molecular Weight

66,437 Da8 (based on amino acid composition). Commercial preparations contain varying degrees of post-translational modifications and genetic variants with molecular weight components mainly in the range of 66,437 to 66,600 Da

Deconvoluted mass spectrum of intact Native HSA

Methods of Preparation

We produce human serum albumin using a cold alcohol fractionation process derived from the traditional Cohn1,3 method as well as heat shock methods.2,4

Structure5

Human albumin is a single peptide chain with one free sulfhydryl group on residue # 34 and 17 intrachain disulfide bonds.

Mass Spec Analysis of various commercial preparations indicates the presence of several post-translational modifications. Native human serum albumin is not a glycoprotein in the traditional sense. However, several genetic variants exist that may undergo enzymatic N-& O-glycosylation. Upon circulation in plasma, albumin often becomes glucosylated on ε amine groups of lysine and possibly arginine residues. This is the result of the non-enzymatic spontaneous Maillard Reaction between the carbonyl group of the open ring form of glucose, present in small amounts in plasma, forming a Schiff base with the exposed primary amines of circulating proteins such as albumin, insulin and hemoglobin. Sigma has also observed various degrees of glucosylation in recombinant preparations. Cysteinylation is also present in native and recombinant preparations.

Amino Acid Composition

 
Amino Acid Asp Asn Thr Ser Glu Gln Pro Gly Ala Cys Val Met Ile Leu Tyr Phe His Lys Trp Arg
Residues 39 15 30 22 60 23 25 12 63 35 39 6 8 61 18 30 16 58 1 23

Fatty Acid Composition of Human Albumin

Circulating plasma albumin typically contains 0.5-1.5 moles of fatty acid bound to one mole of albumin. Upper ranges of 4-9 moles per mole have been reported.9,10 Alternatively, Sigma offers fatty acid depleted native human albumins.

 

Saturated Fatty Acids Native .HSA rHSA expressed in Rice
Lauric 12:0
13:0
<1%
<1%
0.2%
 
Myristic 14:0 1.50% 1.5%
Pentadecenoic 15:0 < 1% 0.1%
Palmitic 16:0
17:0
24.70%
<1%
12.5%
 
Stearic 18:0 1.50% 0.5%
Arachidic 20:0 <1% 0.0%
Bohenic 22:0 Not Tested 0.0%
Lignoceric 24:0 Not Tested 0.0%
Monosaturated Fatty Acids    
Myristoleic 14:1 <1% 0.0%
Palmitoleic 16:1w7 <3.1% 0.8%
Oleic 18:1w9
18:1w7
24:1
<33.1%
<1%
<1%
35.9%
0.0%
0.0%
Diunsaturated Fatty Acids    
Linoleic 18:2w6 <20.0% 44.8%
Polyunsaturated Fatty Acids    
α-Linolenic 18:3w3
18:3w6
20:1w9
20:1w9
20:2w6
20:3
<1%
<1%
<1%
<1%
<1%
<1.40%
3.6%
0.0%
0.0%
0.0%
0.0%
0.0%
Arachidonic 20:4
20:5
22:1w9
22:4w6
22:5w6
22:5w3
22:6w3
5.00%
<1%
<1%
<1%
<1%
<1%
<1%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%

Physical Properties5

 
Sedimentation constant, S20,W X 1013 4.6 (monomer), 6.5 (dimer)
Diffusion constant, D20,W X 107 6.1
Partial specific volume, V20 0.733
Intrinsic viscosity, η 0.042
Frictional ratio, f/f0 1.28
Overall dimensions, Å 38 X 150
Isoelectric point (Γ/2 = 0.15) 4.7
Isoionic point (Γ/2 = 0) 5.2
Electrophoretic mobility, pH 8.6, G/2 = 0.15 -5.9
Refractive index increment (578 nm) X 10-3 1.89
Optical absorbance, A279 nm (1 gram/liter) 0.531
Mean residue rotation, [m']233 8590
Mean residue ellipticity 17 [q]209 nm; 16 [q]222 nm
Estimated α-helix, % 48
Estimated β-form, % 15

Applications and Other Properties7

Due to its high charge to mass ratio, albumin binds water, Ca2+, Na+, K+, fatty acids, bilirubin, hormones and many xenobiotic drugs. The main biological function of albumin is to regulate the colloidal osmotic pressure of blood. Human and bovine albumins contain 16% nitrogen and are often used as standards in protein calibration studies. Due to their free hydrophobic region, fatty acid free albumins are used to solubilize lipids in tissue culture, and are also used as blocking agents in Western blots or ELISA applications. Globulin free albumins are suitable for use in applications where no other proteins should be present (e.g., electrophoresis).

Products

Powders: Native Preparations

Powders: Recombinant Preparations

Solutions: Native Preparations

Solutions: Recombinant Preparations

Protein Standards

Modified HSAs

References

  1. E.J. Cohn, J. Amer. Chem. Soc., 68, 459 (1946).
  2. R.F. Chen, J. Biol. Chem., 242, 173 (1967).
  3. E.J. Cohn, J. Amer. Chem. Soc., 69, 1753 (1947).
  4. Globulins are precipitated in a heat step following addition of caprylate, then removed by filtration.
  5. The Plasma Proteins, 2nd Ed., Vol. I, F. W. Putnam, Ed., pp. 133-181, Academic Press, New York (1975).
  6. S.C. Gill and P.H. von Hippel, Anal. Biochem., 182, 319 (1989).
  7. T. Scott and M. Eagleson, Concise Encyclopedia: Biochemistry, 2nd Ed., pp. 19-20, Walter de Gruyter, New York (1988).
  8. Sigma calculation based on sequence given by B. Meloun, et. al., FEBS Letters, 58(1), 134 (1975).
  9. The free fatty acids bound to human serum albumin. Saifer, A., Goldman, L., J. Lipid Res., 2, 268-270 (1961)
  10. Fatty acid enhancement of human serum albuminbinding properties. J. Biol. Chem., 252, 4043-4048 (1977)