Biotechnology Homework Help: Enzymes Production
Enzymes are obtained from animal tissues, plants, bacteria and fungi, including yeast. The bulk of enzymes, both in terms of quantity and variety, are derived from micro-organism, higher plants being the distant second and animals being the least important. The only animal enzyme to be produced in quantities greater than 2 ton/year is rennet or chymosin obtained from calf stomach. The bulk of plant enzymes are hydrolytic enzymes, e.g. , papain etc. Most of the enzymes are used by food industry. Therefore, according to homework help sites initially, plant and animal enzymes were preferred over microbial enzymes mainly for considerations of safety and the fear of contamination by micro-organisms, toxins etc.
But increased demands, shortages in supplies of enzymes from plant and animal sources, and difficulties in maintaining a continued supply of these enzymes prompted a much closer and more pragmatic evaluation of the microbial enzymes. These enzymes have found increasing applications even in such areas where enzymes of animal origin were once exclusively used, e.g. cheese production. According to answers for homework experts the rennet (= aspartic proteinase) produced by Mucor miehei is now widely used for cheese production, while rennet from calf stomach was exclusively used in earlier days (about 2 decades ago). Microbes as a source of enzymes have the advantage of large scale production by fermentation, ease in isolation of especially those enzymes which are excreted into the medium, e.g. most hydrolases, the variety of enzymes produced and the ease in genetic manipulation to enhance enzyme yields and even to modify the enzyme using, if desired, recombinant DNA technology.
The rate of reaction catalyzed by an enzyme increases linearly with the substrate concentration upto a point, but it soon reaches the maximum value called Vmax beyond which there is no further increase in reaction rate; this is called saturation. In contrast, the rate of a nonenzymatically catalyzed reaction increases linearly over the entire range of attainable substrate concentrations. The phenomenon of substrate saturation is described by the Michaelis-Menten equation given below: Vmax is the maximum rate of reaction, which occurs when the enzyme is saturated with substrate, v is the rate of reaction, [S] is the substrate concentration and Km is Michaelis constant. According to studydaddy this equation can be used to predict the rate of reaction catalyzed by an enzyme at any substrate concentration provided the values of Vmax and Km are known. Km is the substrate concentration needed to obtain a reaction rate equal to ½ Vmax. The substrate concentrations and reaction rates considered in the above equation are always the initial values, i.e. the values at the start of the reaction.
Although few enzymes follow the Michaelis-Menten equation over a wide range of experimental conditions, it is still the most generally applicable equation for describing enzyme catalyzed reactions. The value of Km is characteristic for each enzyme substrate combination, but is independent of the enzyme and/or substrate concentrations. However, Km may be influenced by pH, temperature, ionic strength and other factors.