Protein structure - Pharmaceutical Biotechnology: Concepts and Aapplications - page 16

Table 2.1 Selected examples of proteins. The number of polypeptide chains and amino acid residues
constituting the protein are listed, along with its molecular mass and biological function

No. polypeptide
chains

Total no. amino
acids

Molecular mass
(Da) Protein Biological function

Insulin (human) 2 51 5 800 Complex, includes

regulation of
blood glucose
levels

Lysozyme (egg) 1 129 13 900 Enzyme capable

of degrading
peptidoglycan in
bacterial cell walls

IL-2 (human) 1 133 15 400 T-lymphocyte-

derived
polypeptide
that regulates
many aspects of
immunity

EPO (human) 1 165 36 000 Hormone that

stimulates
red blood cell
production

Chymotrypsin
(bovine)

3 241 21 600 Digestive proteolytic

enzyme

Subtilisin ( Bacillus
amyloliquefaciens )

1 274 27 500 Bacterial proteolytic

enzyme

Tu mou r n e c r o si s
factor (human
TNF-α)

3 471 52 000 Mediator of

infl ammation and
immunity

Haemoglobin
(human)

4 574 64 500 Gas transport

Hexokinase (yeast) 2 800 102 000 Enzyme capable of

phosphorylating
selected
monosaccharides

Glutamate
dehydrogenase
(bovine)

∼40 ∼8 300 ∼1 000 000 Enzyme

interconverts
glutamate and
α-ketoglutarate
and NH +

contain one or more non-polypeptide constituents known as prosthetic group(s). The most com-
mon prosthetic groups found in association with proteins include carbohydrates (glycoproteins),
phosphate groups (phosphoproteins), vitamin derivatives (e.g. fl avoproteins) and metal ions
(metalloproteins).