What is the function of avidin?

Avidin is a biotin-binding protein that is believed to function as an antibiotic in the eggs of birds, reptiles and amphibians. Chicken Avidin has a mass of 67,000-68,000 daltons and is formed from four 128 amino acid-subunits, each binding one molecule of biotin.

Why is avidin bad?

In raw eggs, a protein in the egg whites called avidin binds to biotin, making it unavailable for your body to use. However, when eggs are cooked, the heat causes structural changes to avidin, making it less effective at binding to biotin.

Is avidin an enzyme?

Immunohistochemical staining intensity is a function of the enzyme activity, and improved sensitivity can be achieved by increasing the number of enzyme molecules bound to the tissue.

What kind of protein is avidin found in eggs?

Avidin is a tetrameric biotin-binding protein—or glycoprotein with a molecular weight of approximately 62.4 kDa— that shows high sequence homology in birds, reptiles, and amphibians, and is deposited in the egg white.

How long does it take to inactivate avidin in egg white?

The assay surmised that cooking times were not sufficient to adequately heat all cold spot areas within the egg white. Complete inactivation of avidin’s biotin binding capacity required boiling for over 4 minutes. A 1992 study found that thermal inactivation of the biotin binding activity of avidin was described by D 121 °C = 25 min and z = 33 °C.

What are the biotin binding characteristics of avidin?

Researchers have created an avidin with reversible binding characteristics through nitration or iodination of the binding site tyrosine. The modified avidin exhibits strong biotin binding characteristics at pH 4 and releases biotin at a pH of 10 or higher.

How is avidin created from immobilized native avidin?

The monomeric avidin is created by treatment of immobilized native avidin with urea or guanidine HCl (6–8 M), giving it a lower dissociation K D ≈ 10 −7M. This allows elution from the avidin matrix to occur under milder, non-denaturing conditions, using low concentrations of biotin or low pH conditions.