Therapeutic Proteins from Soy

Linda Benedict, Losso, Jack N.  |  7/28/2011 12:34:03 AM

Jack Losso

Epidemiological observations have consistently shown that incidences and mortality rates of cancers, diabetes, multiple sclerosis, Alzheimer’s disease and several chronic degenerative diseases vary significantly across regions of the world. Populations whose major diets are mainly centered on plant foods tend to have lower rates of these diseases. In the western world, however, the rates of colon, breast and prostate cancers, multiple sclerosis, diabetes and Alzheimer’s disease are high.

The rates of cancer among populations migrating from low- to high-incidence countries can change markedly. In most cases, they approximate the rates in the new region within one to three generations. This indicates that the primary determinants of cancer or other chronic diseases are not genetic but rather environmental and lifestyle factors that could, in principle, be modified to reduce chronic diseases in high-risk individuals. While in most cases genetic determinants appear to affect 5-10 percent of the population, in the last two decades a primary factor of interest, apart from tobacco, has been diet.

Proteases are enzymes that help the body change proteins into substances it needs. They facilitate many normal physiological functions as well as changes that accompany disease or injury. These include digestion, healing, disease defense, blood coagulation and the activation of proteins that are precursors to enzymes and hormones. An imbalance that favors proteases over their inherent inhibitors in the body may trigger the uncontrolled breakdown of proteins, which leads to irreversible tissue destruction, such as inflammation, rheumatoid arthritis, periodontitis, hypertension, gastric ulcers, muscular dystrophy, tumor growth and the spread of cancers.

Proteinase inhibitors, which frequently are involved in chronic diseases, are compounds that deactivate protease and stop their uncontrolled activities. Identifying natural products that can inhibit protease activities is what pharmaceutical industries and food scientists are always searching for.

Soybean seed is a rich source of protein and contains an average of 34.9 percent proteins. Soybean proteins are the "functional parts of soy products, such as soy milk, tofu and soy vegetables. Soybeans also are a rich source of bioactive proteins including the Bowman-Birk inhibitor (BBI) and Kunitz trypsin inhibitor. Both proteins have been extensively investigated for their efficacy against proteinases involved in human diseases.

The uniqueness of soybeans among other legume seeds lies in the ability to contain inhibitors for almost every class of proteinases involved in human diseases. The BBI is a 71-amino acid, water-soluble protein found in most soy products. It is very stable and bioavailable. Several studies have shown its health-enhancing benefits. In cell cultures, BBI is known to inhibit enzymes associated with cancer cell invasion and proliferation. Astronauts on space missions are likely to experience deficiency in blood antioxidants and exposures to space radiation, which significantly increase the incidence rate of malignant lymphoma and rare tumor types, malignant lesions of bone marrow, tumors originating in blood cells and cataracts. In animal models of space exposure, BBI has been shown to counteract these effects.

Tumor cells are often bent and twisted and disconnected from each other, making it difficult for drugs to penetrate and kill all the cells. This disorganized structure has been associated with the reduction or loss of proteins called connexins connexins, which allow adjacent cells to connect. BBI has been shown to counter the loss of connexins in disease cells. The efficacy of BBI in the treatment of ulcerative colitis has been demonstrated in animal models of the disease, and BBI has shown beneficial effects in patients with ulcerative colitis with no side effects. BBI in the form of a concentrate known as BBIC has been used in Phase I, II and III trials as a human cancer-preventive dietary supplement.
Multiple sclerosis is an autoimmune disease whereby inflammation generates proteases that destroy the myelin sheath that insulates nerve cells. Multiple sclerosis is associated with muscle weakness, difficulty with coordination and balance, partial or complete paralysis, and cognitive impairment. Although there is no real cure for multiple sclerosis, available treatments often require frequent injections of anti-inflammatory drugs that have significant side effects. Research has shown that BBI, which penetrates the central nervous system, delays the onset and suppresses the severity of multiple sclerosis in rats and may have application in human therapies.

While BBI is present in soy products, no specific methods are available to measure the levels of BBI in soy products, including soy milk, soy burgers, soy vegetables and tofu. LSU AgCenter researchers have developed an antibody against BBI that will be useful in determining the levels of BBI in soy products.

Jack Losso, Professor, Department of Food Science, LSU AgCenter, Baton Rouge, La.

(This article was published in the spring 2011 issue of Louisiana Agriculture.)

Rate This Article:

Have a question or comment about the information on this page?

Innovate . Educate . Improve Lives

The LSU AgCenter and the LSU College of Agriculture