Soybean, urease

This reaction is catalyzed by a highly specific enzyme, urease. Urease is present in a number of bacteria and plants. The most common source of the enzyme is jack bean or soybean. Urease was the first enzyme that was crystallized. Sumner, in 1926, proved unequivocally that enzymes are protein molecules. 

Arachin, the counterpart of glycinin in peanuts, consists of subunits of 60,000—70,000 mol wt which on reduction with 2-mercaptoethanol yield polypeptides of 41,000—48,000 and 21,000 mol wt (17) analogous to the behavior of glycinin. In addition to the storage proteins, oilseeds contain a variety of minor proteins, including trypsin inhibitors, hemagglutinins, and enzymes. Examples of the last are urease and Hpoxygenase in soybeans. 

The enzyme urease was discovered in soybeans by Takeuchi in 1909 it catalyzed the conversion of urea to ammonium carbonate. Jack beans were another excellent source of the enzyme. Jack bean powder could be stored for considerable periods and very active, soluble, urease extracted. After the action of urease, the ammonia could be estimated colorimetrically by Nesslerisation or titrimetrically. The Conway diffusion apparatus was specially developed for the estimation of urea titrimetrically and remained in use into the 1950s. 

Urease Soybean AOT, CTAB, Triton X-100, mixed AOT-Triton X-100 detergent free micro emulsions (hexane/iso-propanol/water) Solubilization and catalytic studies [81]... 

UREASE. Enzyme present in low-percentages in jackbean and soybean water soluble, its action is inhibited by heavy-metal ions. Its principal use is in the determination of urea in urine, blood, and other body fluids it splits urea into ammonia and carbon dioxide or ammonium carbonate. 

Underheating of whole soybean may fail to destroy the trypsin inhibitor and reduce urease and lipase activity, resulting in low protein efficiency for critical feeds. An underheated soybean meal greatly increases the need for vitamin D to prevent rickets in turkey poults. Overheating of whole soybeans tends to inactivate or destroy the essential amino acids lysine, cystine, and methionine and possibly others (31). 

Laboratory tests such as urease activity, protein dispersibility index (PDI), nitrogen solubility index (NSI), thiamine, and water absorption have been found valuable in monitoring daily production for protein quality. But biological chick and/or rat assays are the only reliable means currently available for predetermining the nutritional value of whole soybean protein they must be conducted periodically to verify results of chemical tests (31). If whole soybeans are to be used in a mixture containing 20% or more soybean meal, 5% or more urea, and 20% or more molasses, or an equivalent mixture, and exposed to hot, humid storage conditions, it is advisable that the urease activity of the whole soybeans not exceed 0.12 increase in pH (31). Extruded or roasted soybeans properly treated for cattle to increase bypass protein should have urease values of less than 0.05 pH rise. A urease rise of 0.05-0.20 is an indication of proper treatment for swine and poultry. 

A 203 mm (8 in.) diameter extruder, powered by a 112-kW (150-hp) motor, can process raw cracked soybean at up to 2722 kg/h (6000 Ib/h). The product, having low levels of urease and trypsin inhibitor, is marketable, without any further processing except cooling, as full-fat soymeal. However, the hot product, flashed down to 5-7% moisture, having almost all the oil cells ruptured, is ready to pass immediately to a screw-press. A conventional screw-press, with some modification to wormshaft configuration and rotational speed, can process this material at a threefold increase in capacity using the same motor and pressing to the same residual oil. 

Soybeans also contain lectins, urease, saponins, goitrogenic factors, rachitogenic factors, allergic factors, and metal chelating factors, all of which can have a negative impact on performance (15). Fortunately, many of these antinutritive factors are heat labile, and adequate heat treatment renders full-fat soybean meal safe for use in nonruminant diets. Hence, given a cost effective means of heat processing, the nutritional potential of this valuable raw material can be unlocked. 

It is this effect of denaturization that is useful when extruding oilseeds. Soybeans have an enzyme, urease, which can be denatured by heat created in the extruder. Enzymes are proteins, and when they are denatured, they lose their effectiveness. Urease breaks down urea to ammonia. 

As expanders cook within 20 seconds, they counteract the activity of troublesome enzymes, such as lipase in rice bran (40) and urease in soybean (41). The short time between enzyme activation and inactivation destroys the enzyme before it has time to cause damage. An expander is even more effective than the horizontal, atmospheric pressure cookers described earlier. 

An eight inch diameter expander, with 150 HP drive, can process preheated, cracked soybean at 60001bs/hr, producing full-fat soy with low levels of urease and trypsin inhibitor. Also, the hot product can pass into a screw-press (after its moisture is allowed to flash to 5-7%). As most of the oil cells have been ruptured by the expander, a screw-press can process the soybean at three times the capacity it would have had with unexpanded soybean. 

Wang and Johnson (2001) reported on test measurement methods that were major indicators of soybean oil quality. These tests included peroxide value, anisidine value, FFA content, phospholipid content, total tocopherol content, oxidative stability index, color, and moisture content. For soybean meal, they reported on urease activity, protein dispersibility index (PDI), rumen bypass or rumen undegradable protein, trypsin inhibitor activity, moisture content, residual oil content, protein content, fiber content, color, amino acid profiles, and protein solubility under alkaline (KOH) conditions. 

More than 97% of the available soybean meal is used for feed where extensive heat treatment is necessary to maximize feed conversion efficiency by livestock. Toasting inactivates protease inhibitors (especially trypsin and chymotrypsin inhibitors) and the enzyme urease, and improves protein digestibility. None of these objectives can be obtained without protein being denatured and loss in water solubility however, depending on the method used, meals with great differences in protein solubilities or dispersibilities can be produced. The optimum amount of heat treatment in toasting soybean meal is still debated among animal nutritionists. 

Urease 3.5.1.5 Jack bean Lemna paucicostata Rumen bacterial Soybean... 

Folacco, J.C. Nitrogen metabolism In soybean tissue culture. II. Urea utilization and urease synthesis require Nl " ". Plant Physiol.. 1977, 59, 827-830. 

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