Enzyme in nature

Pathogenic organisms possess certain properties which enable them to overcome these primary defences. They produce metabolic substances, often enzymic in nature, which facilitate the invasion of the body. The following are examples of these. 

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

When the anomeric hydroxyl group of one monosaccharide is bound glycosidically with one of the OH groups of another, a disaccharide is formed. As in all glycosides, the glyco-sidic bond does not allow mutarotation. Since this type of bond is formed stereospecifically by enzymes in natural disaccharides, they are only found in one of the possible configurations (a or P). 

Aminotransferases are widely distributed enzymes in nature, participating in a number of metabolic pathways (7-11). They catalyze the transfer of an amino group originating from an amino acid donor to a 2-ketoacid acceptor. In effect, this statement implies the reductive animation of a keto moiety, although a redox process is not directly involved. 

There are two attributes of a-D-mannosidase (EC 3.2.1.24) that receive particular attention in this article, namely, its behavior as a zinc-containing metalloenzyme, and its action on naturally occurring, D-mannose-containing molecules. However, such more-systematic considerations as the kinetics of action and the distribution of the enzyme in Nature are not overlooked. 

All restriction enzymes are named after the bacterium W here they originated. The Cutting sites (restriction sites are also named, and they bear the same name as the relevant enzyme. Table H.f shows several commonly used restriction enzymes, the structures of the target site that is hydrolyzed by the enzyme, and the organisms that originally produced the enzymes in nature (Bhagw at, 1992). 

Enzymes in nature can evolve much faster under certain conditions, e.g. in contaminated soils. An example is a phosphotriesterase, an enzyme discovered in a soil bacterium, which degrades certain pesticides. It is believed that this enzyme evolved during the last 50 years from a homologous sequence in the E. coli bacterium. Scanlan TS, Reid RC (1995) Chem Biol 2 71... 

Often extracellular enzymes in natural waters are induced by a low concentration of a necessary substrate. For example, some deaminases and phosphatases are induced in phytoplankton when inorganic nitrogen and phosphorus are scarce, so as to use organic nutrient sources. Further, the enzymatic system may be made more efficient if the substrate itself (e.g., the organic nutrient) becomes low. 

The few examples considered in this chapter demonstrate the wide range of chemistry available to flavins, and the large number of enzyme catalysts possible by the combination of the various half-reactions. The enzymes in nature have evolved to accelerate the chemistry of their half-reactions and suppress unwanted side reactions, enabling flavoenzymes to participate in most areas of biochemistry. 

There are thousands of enzymes in nature, and most of these exhibit absolute specificity. 

Sign in atwww.thomsonedu.com/login and explore a Biochemistry Interactive tutorial on the structure of rubisco,the principal COj-fixing enzyme in nature. 

Leucine aminopeptidase reacts slowly with Mg++ or Mn++ to form an active enzyme. The rate and extent of activation are functions of metal concentration. The combination with Mn++ is faster than that with Mg++, and results in greater ultimate activity. Nevertheless, the fact that citrate inactivates crude preparations of the enzyme indicates that Mg++, not Mn++, is associated with the enzyme in nature. Citrate inhibits the Mg++-activated, but not the Mn -activated enzyme. The formation of active enzyme is apparently a simple reversible reaction in which one atom of metal combines with one molecule of protein. A dissociation constant could be calculated for the enzyme-Mn combination by measuring the rate of hydrolysis of L-leucinamide as a function of Mn" concentration. The resulting data fit the equation... 

It is of interest that, in addition to their enzymic content, mitochondria possess fats and lipoids, and naturally not all their protein is enzymic in nature. In addition, mitochondria are not permanent they can be substantially reduced in numbers by starvation. Therefore we might simply consider them, as Bensley does, as a reserve store of metabolic material on which the cell can draw in time of need. Such structures provide suitable surfaces for the adsorption and possible absorption of various enzymes. Once such enzymes are incorporated into the mitochondria the latter are then able to control the metabolic processes of the cell by presenting more or less surface to the cytoplasm. 

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