Gene ID: ALB
Methods of Preparation:
Sigma-Aldrich produces human serum albumin using a cold alcohol fractionation process derived from the traditional Cohn1,3 method as well heat shock methods.2,4
66,437 Da 8 (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
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
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.
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).