Chymotrypsin is synthesized by protein biosynthesis as a precursor called chymotrypsinogen that is enzymatically inactive. On cleavage by trypsin into two parts that are still connected via an S-S bond, cleaved chymotrypsinogen molecules can activate each other by removing two small peptides in a trans-proteolysis. The resulting molecule is active chymotrypsin, a three polypeptide molecule interconnected via disulfide bonds.

Action and Kinetics of chymotrypsin

In vivo, chymotrypsin is a proteolytic enzyme acting in the digestive systems of mammals and other organisms. It facilitates the cleavage of peptide bonds by a hydrolysis reaction, a process which albeit thermodynamically favourable, occurs extremely slowly in the absence of a catalyst. The main substrates of chymotrypsin include tryptophan, tyrosine, phenylalanine, and methionine, which are cleaved at the carboxyl terminal. Like many proteases, chymotrypsin will also hydrolyse ester bonds in vitro, a virtue that enabled the use of substrate analogs such as N-acetyl-L-phenylalanine p-nitrophenyl ester for enzyme assays.

Chymotrypsin cleaves peptide bonds by attacking the unreactive carbonyl group with a powerful nucleophile, the serine 195 residue located in the active site of the enzyme, which briefly becomes covalently bonded to the substrate, forming an enzyme-substrate intermediate.

These findings rely on inhibition assays and the study of the kinetics of cleavage of the aforementioned substrate, exploiting the fact that the enzyme-substrate intermediate p-nitrophenolate has a yellow colour, enabling us to measure its concentration by measuring light absorbance at A400.

It was found that the reaction of chymotrypsin with its substrate takes place in two stages, an initial “burst” phase at the beginning of the reaction and a steady-state phase following Michaelis-Menten kinetics. The mode of action of chymotrypsin explains this as hydrolysis takes place in two steps. First acylation of the substrate to form an acyl-enzyme intermediate and then deacylation in order to return the enyzme to its original state.

Reference

Stryer et. al. (2002). Biochemistry (5th ed.). New York: Freeman. ISBN 0-7167-4684-0.

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Self-help booklet
From Townsend Letter for Doctors and Patients, 7/1/05 by Jule Klotter

Cancer's Best Medicine, a 48-page booklet by Mauris L. Emeka, explains what cancer cells need in order to thrive and, conversely, what kind of environment will inhibit their growth. A deficiency of pancreatic enzymes, specifically trypsin and chymotrypsin, encourages cancer growth, according to the work of Scottish embryologist John Beard. Beard discovered almost a hundred years ago that these protein-digesting enzymes prevent undifferentiated trophoblast cells from growing unchecked and forming tumors. Unlike fresh raw food, processed food contains no digestive enzymes. People who eat mostly processed food and a lot of animal protein risk overworking the pancreas and depleting their supply of enzymes. Emeka suggests eating enzyme-rich raw fruits, especially papaya and pineapple, and, perhaps, taking pancreatin as a supplement.

A deficiency of pancreatic enzymes is only part of the puzzle; oxygen and acidity are another part. Cancer cells, unlike normal cells, thrive in a low-oxygen, acidic environment--and they love simple sugars. Dr. Otto Warburg discovered that cellular oxygen is a key factor in preventing cancer. Healthy cells only use anaerobic metabolism (cancer's preferred way to make energy) when cellular oxygen levels become low. During anaerobic metabolism, lactic acid forms, creating an inviting acidic terrain for cancer growth. With abundant cellular oxygen levels, normal cells create energy more efficiently and maintain a healthy pH level. In his self-help booklet, Emeka recommends eating plenty of dark green leafy vegetables (i.e., collard greens, turnip greens, kale, and Swiss chard) each day. The high chlorophyll content in these vegetables "enhances the circulation of oxygen at the cellular level and it contributes greatly to normalizing body pH by making it less acidic and more alkaline." Drinking plenty of water and a practice of deep breathing and physical exercise also bring more oxygen into the body.

In addition to these recommendations, Cancer's Best Medicine suggests specific foods and other simple lifestyle actions that promote health and stimulate the immune system. Emeka urges patients to remember that while "cancer is a serious health condition ... cancer is not your life, it is not the essence of who you are." Cancer's Best Medicine is available from Apollo Publishing International, P.O. Box 1937, Port Orchard, Washington 98366 (phone 360-876-5376) for $6.00. Emeka, Mauris L. Cancer's Best Medicine--A Self-Help and Wellness Guide (Apollo Publishing International, 2004)

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