Introduction
Protease refers to a group of enzymes whose catalytic function
is to hydrolyze (breakdown) peptide bonds of proteins. They are
also called proteolytic enzymes or proteinases. Proteases differ
in their ability to hydrolyze various peptide bonds. Each type of
protease has a specific kind of peptide bonds it breaks. Examples
of proteases include: fungal protease, pepsin, trypsin, chymotrypsin,
papain, bromelain, and subtilisin.
Proteolytic enzymes are very important in digestion as they breakdown the protein foods to liberate the amino acids needed by the body. Additionally, proteolytic enzymes have been used for a long time in various forms of therapy. Their use in medicine is gaining more and more attention as several clinical studies are indicating their benefits in oncology, inflammatory conditions, blood rheology control, and immune regulation.
Contrary to old beliefs several studies have shown that orally
ingested enzymes can bypass the conditions of the GI tract and be
absorbed into the blood stream while still maintaining their enzymatic
activity. Commercially, proteases are produced in highly controlled
aseptic conditions for food supplementation and systemic enzyme
therapy. The organisms most often used are Aspergillus niger
and oryzae.
Proteases As Scavengers of Oxidized and Damaged Proteins
Oxidative reactions generate free radical damage to various molecules
including proteins. Free radicals have been implicated in accelerating
the aging process as well as several diseases, including diabetes,
atherosclerosis, and neurodegenerative conditions. Under proper
conditions of nutrition and adequate activity of antioxidant enzymes,
the free radical damage is minimized. However, in many instances,
the body is overwhelmed by the load of proóoxidants (free radical
generating molecules), resulting in oxidative stress.
One consequence of oxidative stress is the formation of oxidized proteins. Oxidized proteins often loose their function (become inactive), and undergo unfolding or conformational change of their structure which enhances their susceptibility to proteolysis. For instance, oxidized proteins in blood or extra cellular fluid, include hormones, immune system proteins, transport proteins, and other proteins needed at various cellular locations.
As these oxidized proteins lose their biological function, they may not carry
out the cellular tasks and biochemical reactions they are meant
to perform For instance, an oxidized hormone may not be able to
attach to its receptor on the cell surface; an oxidized enzyme may
not perform its activity; an oxidized antibody molecule will not
bind adequately to its antigen.
Oxidative reactions occur in a cascade manner. Therefore, oxidation of one protein may lead to further oxidation reactions within the same molecule and/or other molecules which amplify the damaging effect. The oxidation of a protein, if not corrected, may result in impairment of biochemical functions of vital importance to the cellular viability. In order to avoid the cascade effect, oxidized proteins may be reduced by an antioxidant enzyme or vitamin to their normal (native) form, or removed by proteolysis.
Oral proteases taken on an empty stomach have been shown to be absorbed and carried into the blood stream where they are bound to Alpha2-macroglobulin. The binding of the Alpha2-macroglobulin to proteases does not inactivate the proteolytic activity of the protease. However, the complexing of the Alpha2-macroglobulin ensures the clearance of the protease from the organism. Several studies have indicated that oral proteases bound to the macroglobulins hydrolyze immune complexes, proteinaceous debris, damaged proteins, and acute phase plasma proteins in the blood stream' It is suggested that oral proteases may help hydrolyze and remove extra cellular proteins damaged by free radicals, which are especially susceptible to proteolysis, as mentioned above.
Heavy Metals and Oral Fungal Protease
Heavy metals, such as lead (Pb) and mercury (Hg), exert their poisoning
effect by binding to ionizable or sulfhydryl groups of proteins,
including vital enzymes. Once they bind to an essential functional
protein, such as an enzyme, they denature and/or inhibit it. This
interaction of heavy metals to proteins can lead to degenerating
diseases, nerve damage or even death.
Clinical observations have noted that upon high intake of oral protease, heavy metal concentrations have been significantly decreased in the blood. Binding of protease to Alpha2-macroglobulin leads to activated complex with altered binding affinities and an increased rate of clearance from the blood by the liver. It is possible that the activated (Alpha2- macroglobulin protease complex also has a high affinity for heavy metals, leading to their removal from the body.
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