Monday, February 16, 2009

Extraction & Purification of Proteins

Biochemists investigate proteins at different levels. At the simplest level they carry out qualitative chemical tests to find out if samples of material contain protein of any sort. At the other extreme they can use the most up-to-date technology to find out the precise arrangement of every atom in each molecule of a particular protein. For structural elucidation, proteins should be very pure homogeneously and in some cases they should be crystallized. There are various methods of extraction and purification of proteins from different sources such as microbes and plant and animal tissues. Extraction and separation techniques for the purification of compounds from microbial cultures and plants and animal tissues are collectively called downstream processing. For industrial purposes, there are some microorganisms identified as non-pathogenic, non-toxic which do not produce any antibiotic. These microorganisms can be used as a source of industrial enzymes and proteins as well as for introducing foreign genes for producing recombinant proteins. Such microorganisms are called generally regarded as safe (GRAS) microbes.

Plants and some animal tissues such as pancrease form the source of some important industrially important proteins and enzymes, which are used in food industry and medicine. Such enzymes should be extracted from non-toxic plant parts and the animal tissues used should be free from infectious diseases. For example, one of the important industrial enzymes, papain, is extracted from the latex of green leaves and fruits of papaya. Papain is used in the meat industry and leather industry for meat tenderization, processing the collagen and other fibrous proteins present in leather, clarification of beverages, and also in medicines as a digestive aid and for cleaning wounds.

Proteins and enzymes of animal origin can be extracted and purified from the respective organs in which the enzyme is present in higher quantities. Slaughterhouses are one of the centers for the supply of tissues and organs necessary for the extraction of certain proteins such as insulin. Traditionally, insulin was obtained from the pancreas of cows and pigs. It requires the slaughtering of about 100 to 150 pigs or 15 to 20 cows to meet the insulin requirement of a single diabetic patient per year. From this we can imagine the number of animals that have to be killed to meet insulin requirements. But modern biotechnology and genetic engineering has come in to help the situation.

Nowadays we don't depend on animals for insulin. There are a number of pharmaceutical companies which manufacture and market human insulin produced by genetic engineering. Similarly, a large number of therapeutic proteins such as vaccines and hormones are now produced by genetic engineering. Today, efforts are there to produce transgenic plants and animals capable of producing these therapeutic antibodies and hormones, and other industrially important proteins in specific organs of plants and animals. For example, the production of edible vaccines (edible plant parts such as fruits and tubers containing the vaccine) and expression of certain proteins such as insulin in the milk of cows and goats, and in eggs. This method of genetic engineering for large-scale production of specialized proteins and other molecules is called molecular farming. The main advantages of molecular farming is that the cost of production can be reduced, costly and time-consuming fermentation procedures and downstream processes can be avoided, large-scale production of the specific compounds is possible, and ease of production and purification procedures is advantageous.

Edible vaccines have the advantage that they can be stored for a long time without refrigeration, can be easily transported, and can be administered by feeding the fruit or the plant parts having the vaccine. While eating the vaccinated fruit, the vaccine molecules will be absorbed into the bloodstream through the mucous membrane lining the mouth and esophagus. Even animals can be vaccinated by this way. Attempts are being made to develop transgenic fodder grass containing the anthrax vaccine. Cattle can be fed with this transgenic fodder grass and be vaccinated effectively against anthrax.

Tags: Bio Technology, Bio Genetics, Proteins

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