From the ancient days when blood letting was used as a way of removing the disease-causing agent, we have come a long way in understanding the human body. Enzymes are the most prevalent biomolecules found in the body, which regulate the biochemical reactions inside every living cell.

Thus any disorder or deficiency afflicting the body will have an effect on the enzymes and vice-a-versa.

The vast majority of pharmaceutical products are compounds derived from synthetic chemical processes, from naturally occurring sources (plants, microorganisms), or combinations of both. such compounds are used to regulate essential bodily functions or to combat disease-causing micro-organisms.

Increasing attention is now beingdirected to the body's own regulatory molecules, which occur normally only in very small concentrations and have predominantly defied modern methods of extraction or synthesis.

The most important class of regulatory molecules in the body are enzymes. Enzymes, like other proteins, consist of long chains of amino acids held together by peptide bonds.

They are present in all living cells, where they perform a vital function by controlling the metabolic processes, whereby nutrients are converted into energy and new cells. Moreover, enzymes take part in the breakdown of food materials into simpler compounds.

As commonly known, enzymes are found in the digestive tract where pepsin, trypsin and peptidases break down protein into amino acids, lipases split fats into glycerol and fatty acids, and amylases break down starch into simple sugars.

Enzymes are bio-catalysts, and by their mere presence, and without being consumed in the process, enzymes can speed up chemical processes that would otherwise run veryslowly. After the reaction is complete, the enzyme is released again, ready to start another reaction.

In principle, this could go on forever, but in practically most catalysts have a limited stability, and over a period of time they lose, their activity and are not usable again. Generally, most enzymes are used only once and discarded after, they have done their job.

Enzymes are very specific in comparison to inorganic catalysts such as acids, bases, metals and metal oxides. Enzyme can break down particular compounds. In some cases, their action is limited to specific bonds in the compounds with which, they react.

The molecule(s) that an enzyme acts on is known as its substrate (s), which is converted into a product or products. A part of large enzyme molecule will reversibly bind to the substrate(s) and then a specialised part(s) of the enzyme will catalyse the specific change necessary to change the substrate into a product.

For each type of reaction in a cell there is a different enzyme and theyare classified into six broad categories namely hydrolytic, oxidising and reducing, synthesising, transferring, lytic and isomerising. During industrial process, the specific action of enzymes allows high yields to be obtained with a minimum of unwanted by-products.

Enzymes can work at atmospheric pressure and in mild conditions with respect to temperature and acidity (pH) . Most enzymes function optimally at a temperature of 30ø C-70ø and at pH values, which are near the neutral point (pH 7). Now-a-days, special enzymes have been developed that work at higher temperatures for specific applications. Advances in the knowledge of the uses of enzymes have heightened interest in the manufacture and processing of these macromolecules.

Therapeutic uses of proteolytic enzymes were attempted in the early 19th century, in 1902. Emmerich first demonstrated the therapeutic application of nucleate capable of degrading nucleic acids.

This milestone opened the way for the use of enzymes, first as crude topical andpreparations with proteolytic activity, and later as purified protein for use in cancer chemotherapy, genetic metabolic deficiencies, clotting disorders and as antidotes to treat poisons, drug toxcity, kidney failure.Limited expression of enzymes in the body forced early medical professionals to derive these molecules from organs of cadavers and from blood banks.

Genetic engineering is now increasingly being recognised as a practical means of providing some of these scarce molecules in unrestricted quantities. In practice, this involves inserting the necessary human-derived gene construct into a suitable host microorganism that will produce the therapeutic enzyme in quantities related to the scale of operation.

Not only is it now possible to produce these enzymes in a form identical to that normally occurring in the human body, but also to design meaningful improvements in activity, stability or bioavailability. Crude enzyme extracts are often unsuitable for the therapeutic uses because of theirantigenicity, contamination with endotoxins, and rapid inactivation under physiological conditions or in fluids intended for intravenous infusion over several hours.

Immobilised, modified and entrapped enzyme preparations have become available to circumvent some of the side effect inherent in the use of foreign or immunogenic proteins.

The successful development of therapeutic enzymes requires : a) advanced biochemical / biomedical research to identify and characterise the native compounds, b) skilled molecular biology and cloning technology to identify the relevant gene sequences and insert them into a mammalian or microbiological cell c) bioprocess technology to grow the organism and to isolate, concentrate and purify the chosen compounds d) clinical and marketing expertise. A large number of Indian research institutes and pharmaceutical companies are competent enough to take up the development of enzymes for application in the medical diagnosis and treatment field. Some large pharmaceutical MNCs andalso a couple of Indian biotech companies are looking to enter this hi-tech field.

Commercial enzymes are available in oral form, sometimes formulated with suitable stabilisers and excipients. However, such preparations are seldom suitable for parental use. Therefore, dry preparations devoid of high salt, excipients, or reducing agents have been adopted for final formulation of therapeutic enzymes intended for systemic administration.

The overall world enzyme market is of several billion dollars. However, the contribution of therapeutic enzymes is comparatively very less. This is going to change, with billions of dollars being spent into research in the field of medical biotechnology. A shift is already evident from the use of small molecules in medical therapy to the introduction of peptide and protein drug research.

There has been a steady growth in the economic importance of therapeutic enzymes, with sales reaching hundred of millions of dollars per year.Despite the magnitude of use of these enzymeproducts, the manufacture and sale of the therapeutic enzymes represent a comparatively small fraction of the production and profits of the pharmaceutical houses that market them.

(The authors work with Biotechnology Resource Centre)