Webster's New World Medical Dictionary

protease
An enzyme that can split a protein into
the peptides from which it was originally created.
protease inhibitor
An agent that can keep a
protease from splitting a protein into peptides.
Examples of protease inhibitors are saquinavir
(brand name: Invirase) and ritonavir (brand name:
Norvir), and they are used primarily in HIV/AIDS
treatment. They are taken as part of a multi-drug
cocktail and have been shown to be capable of sig-
nificantly reducing the level of HIV virus in the
blood. Side effects associated with protease
inhibitors include lipodystrophy syndrome, in
which the face, arms, and legs become thin due to
loss of subcutaneous fat; the skin becomes dry;
weight loss occurs; and abnormal deposits of fat
occur. Some strains of HIV may be resistant to pro-
tease inhibitors.
protein
One of the three nutrients used as energy
sources (calories) by the body. Proteins are essen-
tial components of the muscle, skin, and bones.
Proteins and carbohydrates each provide 4 calories
of energy per gram, whereas fats provide 9 calories
per gram.
protein, C
-
reactive
See 
C
-
reactive protein.
protein, G
See 
G protein.
protein C
A vitamin K–dependent protein in
plasma that enters into the cascade of biochemical
events leading to the formation of blood clots.
protein C deficiency
A deficiency of the antico-
agulant protein C, that results in thrombotic (clot-
ting) disease and excess platelets, and recurrent
inflammation of the vein that occurs when a clot
forms (thrombophlebitis). The clot can break loose
and travel through the bloodstream, causing dam-
age to organs including stroke and heart attack.
Protein C deficiency is due to one of numerous
mutations in the protein C gene on chromosome 2.