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Functional Additives
Friday, June 04, 2004 10:08:00 AM
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Enzyme Characteristics and Enzyme Properties
Technical Department

Kemin Europa nv



An Enzyme Is A Protein Which Has To Maintain Its Structure In Order To Function

Enzymes are proteins, which are all composed of various amino acids. Sometimes more than 100 amino acids are joined together to form the protein or the enzyme molecule. These amino acids are arranged in a specific order. There are 20 essential amino acids. This means that a lot of combinations can be made which results in the existence of an enormous number of different enzymes. The chain of amino acids is not a straight one. There are a lot of curves and internal bonds present. Therefore, each enzyme has a strict three-dimensional structure (Figure 1); When this spatial structure is destroyed, the enzyme is unable to function. External conditions that denature the three-dimensional structure (destroy the enzymes) are temperature, pH, UV radiation and certain

chemical compounds.


FIGURE 1: An example of an enzyme constructed out of 107 amino acids.  Internal bonds are shown in black. These bonds can be destroyed by chemical agents.  The result is the unfolding of this three-dimensional structure.  This would mean then that the enzyme is not able to function anymore.





Each Enzyme Catalyses A Specific Reaction


The presence of a large number of enzymes is essential because every biochemical reaction is controlled by enzymes. Each enzyme catalyses a specific reaction. Many reactions do not take place unless there is the right enzyme present.  The precise mode of action of an enzyme can be to split a large molecule, to combine two molecules, to derivatise a basic compound or it can just be the removal of one functional group. There are enzymes that specifically destroy the alpha-bonds in a molecule. Alpha-amylase splits the alpha-bonds in starch. Other enzymes split beta-bonds. Beta-glucanase breaks down glucans and cellulose breaks down cellulose (Fig. 2) Enzymatic activity is necessary for the breakdown of carbohydrates (or polysaccharides) during digestion by an animal. After destruction of those long chain sugars, disaccharides (maltose and cellobiose) and glucose units are formed (Fig. 2) which can easily be absorbed by the animal.


The Highest Enzyme Activity Occurs At Optimal pH And Temperature Conditions

The three-dimensional structure of an enzyme can change with the temperature and the pH. This means that the enzyme activity is strongly related to pH and temperature. Each enzyme has an optimal activity at a specific pH and/or a specific temperature (Fig. 3). Mostly this optimal enzyme activity is spread over a broad area of pH and temperature, but for some enzymes it can be very narrow.



FIGURE 2: In amylose, which is the form of starch with a linear structure, glucose units are linked by alpha-bonds while cellulose (and glucans) consists of long chains of glucose units which are connected by beta-bonds


FIGURE 3: Influence of temperature (A) and acidity (B) on enzyme activity



Each Enzyme Recognizes A Specific Substrate


Enzyme specificity can be best demonstrated by the lock and key model.  Each enzyme has an area that fits exactly to the substrate.  This area which has a strict sequence of amino acids, is called the active site (Fig. 4).  When this sequence is destroyed, the enzyme loses activity.  It is obvious that the maintenance of the three-dimensional structure of the enzyme is important for the recognition of the substrate.


FIGURE 4: Specific recognition between enzyme and substrate (lock and key model)




The Presence Of A Small Amount of Specific Enzymes Is Enough To Catalyse Many Reactions

At optimal conditions only a few enzyme molecules need to be present in order to carry out all the specific reactions. This catalytic specificity can be explained by the fact that the enzyme molecule is released form the enzyme-substrate complex (ES), as soon as the specific action of the enzyme is completed (Fig. 5). The enzyme molecule is then available for the binding of a new substrate molecule, to carry out another cycle of the reaction.

FIGURE 5: Catalytic specificity of enzymes




Enzymes Can Be Produced By Micro-Organisms Such As Fungi, Bacteria And Yeast


This is an important factor. Most commercial enzymes are naturally produced products that can help in industrial reactions or when they are added to the animal feed they can enhance animal performance. Therefore, enzymes are often called natural growth promoters. Furthermore, when the term ¡¡ãprobiotics¡¡À is taken in a broad sense, enzymes belong to the class of probiotics. Enzymes are the metabolites of fermentation products derived form living organisms, such as bacteria, yeasts and fungi. When the origin of enzymes is taken into account, it is easy to understand that an enzyme product has a predominant function but that there are also some side-activities. For example, an alpha-amylase product can be claimed to have high alpha-amylase activity; but when the product is checked carefully it is possible that besides the alpha-amylase activity also some minor beta-glucanase activity is present.


Measurements Of Added Enzyme Activity In Animal Feed Can Be Very Difficult, Due To The Presence Of Sugars And Endogeneous Enzymes

Classical enzyme quantification methods are usually a combination of viscometry, spectrophotometry and titration-dosimetry. The presence of reducing sugars in feed can interfere with these assays and will result in a high background. This would then lead to false interpretations of the results.  Also the presence of natural enzymes or endogeneous enzymes can interfere with the method. The natural enzyme activity can compete with the real added enzyme activity in such a way that no positive effect can be seen after addition of enzymes to animal feed. Therefore, it is important to be able to demonstrate the increase in activity due to the added enzymes.


Enzymatic Digestion Of Feed Is Necessary In Pigs And Poultry Because They Do Not Produce Enzymes To Breakdown Carbohydrates Such As Beta-Glucans And Cellulose

In animal feed many indigestible carbohydrates are present, such as cellulose, beta-glucans, pentosans, starch, hemicellulose, pectins. All these polysaccharides can be broken down by enzymatic activity.  However, the enzyme system in young animals takes some time for the system to function optimally (Fig. 6).



FIGURE 6: Total amylase and proteinase activity in the piglet's pancreas

and intestine in relation to the age




It has been shown that during this period of development, that addition of enzymes to the animal feed will solve most of the digestion problems. Moreover, animals like swine and chickens do not have all the necessary enzymes. They do not themselves produce cellulose and beta-glucanase, which are very important to breakdown cellulose and beta-glucans. Addition of enzymes seems to be a logical solution in this case. Because good digestion requires an optimal use of the potential nutrients present in the feed. This can lead to a better performance of the animal, lower food conversion, less sticky droppings, better health and an increase in resistance against disease.



When Adding Enzymes Into Animal Feed, Shelf-Life And Heat Stability Are Predominant Characteristics To Consider


One of the biggest problems with enzyme products is maintenance of the stability during storage.


Enzymes are proteins and therefore they are influenced by temperature. Normally, proteins are destroyed at temperatures above 60ºC.  When enzyme products are not stored in optimal conditions, loss of activity will occur. Therefore it is important to select enzymes with a high heat stability.


Problems will also arise when the enzyme-treated animal feed has to be pelleted. The extreme conditions during the pelleting process can cause the denaturation of the added enzymes.  The use of heat stable enzymes is obviously an important factor.


Studies of the recovery and demonstration of enzyme activity in pelleted animal feed is an important area of research. With newly developed techniques it is possible to recover the enzyme activity of the KEMZYME® product after pelleting2.


KEMZYME® Is A Dry Stabilized Source Of Different Enzymes With An Optimal Activity Between A pH Range Of 4-7


KEMZYME® is an enzyme product with different activities: alpha-amylase, beta-glucanase, cellulose, lipase and protease.


In the animal digestive tract pH is changing from 2 - 7 (Table 1). Therefore, the enzymes in KEMZYME® are selected for optimal activity at a more acid pH-range (4 - 7).


Enzymes can be in the form of liquids, powders or granulates.  Each form has its own characteristics. The role of enzymes is clear but sometimes it is difficult to point out which one has to be used in a particular feed. Each feed has its characteristic composition based on a large number of ingredients. Only the main ingredients need to be considered because, they contain the largest percentages of indigestible nutrients which can be broken down by the right enzymes. Theoretically, with a well-balanced enzyme mixture it should be possible to improve the use o various feed ingredients. KEMZYME® is the well-balanced enzyme mixture that will make the difference.


TABLE 1: Ranges of pH found in gastrointestinal tract of poultry and pigs


1The stability of KEMZYME® in laboratory trials, KEMIN Research Info Ref. Nr. EZ/K/26


2Heat stability of KEMZYME® DRY during feed manufacture, KEMIN Research Info Ref. Nr. EZ/K/28



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