Soybean enzyme activity

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

Inhibition and stimulation of LOX activity occurs as a rule by a free radical mechanism. Riendeau et al. [8] showed that hydroperoxide activation of 5-LOX is product-specific and can be stimulated by 5-HPETE and hydrogen peroxide. NADPH, FAD, Fe2+ ions, and Fe3+(EDTA) complex markedly increased the formation of oxidized products while NADH and 5-HETE were inhibitory. Jones et al. [9] also demonstrated that another hydroperoxide 13(5)-hydroperoxy-9,ll( , Z)-octadecadienoic acid (13-HPOD) (formed by the oxidation of linoleic acid by soybean LOX) activated the inactive ferrous form of the enzyme. These authors suggested that 13-HPOD attached to LOX and affected its activation through the formation of a protein radical. Werz et al. [10] showed that reactive oxygen species produced by xanthine oxidase, granulocytes, or mitochondria activated 5-LOX in the Epstein Barr virus-transformed B-lymphocytes. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Purple acid phosphatase (PAP) or tartrate-resistant phosphatase is not thought to be a protein phosphatase but it has a very similar dimetallic active site structure to that found in protein phosphatases. PAPs have been identified in bacteria, plants, mammals, and fungi. The molecular weights (animal 35 kDa, plant 55 kDa) are different and they exhibit low sequence homology between kingdoms but the residues involved in coordination of the metal ions are invariant. " There has been considerable debate as to the identity of the metal ions in PAPs in vivo. Sweet potato, Ipomoea batatas, has been shown to possess two different PAP enzymes and the active site of one of them has been shown to contain one Fe and one Zn " " ion. Another report has established that the active site of a PAP from sweet potato contains one Fe " and one Mn +. The well-characterized red kidney bean enzyme and the soybean enzyme contain Fe " and Zn. Claims that PAP from sweet potato has 2Fe ions or 2Mn ions have been discussed elsewhere. One explanation is that these are different forms of the enzyme, another is that because the metal ions are labile and are rapidly incorporated into the active site, the enzyme contains a mixture of metal ions in vivo and the form isolated depends on the conditions of isolation. 

In general, the effects of an acute ozone exposure on plant metabolism will be illustrated using data from soybean, cv. Dare. The soybeans were exposed to ozone for two hr when the first trifoliate leaf was 50 to 60% expanded and analyzed for various metabolites and enzyme activities at 0, 24, 48 and 72 hr following termination of exposure. To illustrate the effects of chronic ozone exposures, data from Ponderosa pine seedlings will be used. Ponderosa pine were grown from seed under field conditions and exposed to 200 yg/m of ozone 6 hr per day throughout the growing season. Harvests were made at monthly intervals after the initiation of exposure. 

Sugars can be metabolized by either glycolysis or by the pentose phosphate pathway. The activities in these pathways can be determined by measuring the enzyme activities of selected dehydrogenases in each path. In soybean, ozone can alter the... 

Presently, the most promising raw material for commercial production of chitinase (in terms of cost per unit activity and ready availability to satisfy present and future demand) is soybean seeds. Table I shows a comparison of cost (based on the retail prices) for the production of chitinase from microbial sources by three commercial suppliers and from soybean seeds. The cost is very high for the commercially prepared enzyme. The method used to purify the soybean enzyme (33) has an average yield of 3.6 I.U./kg or 3600 I.U./metric ton soyEean seeds. The cost for producing 3600 I.U. chitinase from the three suppliers has been calculated and shown in Table I. The Sigma ana Calbiochem-Behring preparations contained the lowest specific activities. 

The assay was demonstrated to be suitable for measurement of enzyme activity in extracts prepared from Azotobacter vinelandii and soybean nodules. 

Considerable purification of lipoxygenase from soybeans was achieved by Balls et al (15), They used conventional protein purification methods and the carotene oxidase reaction to follow the enzyme activity. Theorell et al, (16), in 1947, crystallized the enzyme, or more correctly, one of the several isoenzymes in soybean. We believe this was lipoxygenase-1 as described later. 

The impact of enzyme activity on the nonhydratable phospholipid content of crude soybean oil was investigated by List et al. (140). Evaluation of flakes subjected to live steam and whole beans treated by microwave heating to inactivate phospholipase D suggests that heat, moisture, and enzyme activity are important factors contributing to the formation of nonhydratable phospholipids in extracted crude oils. Approximately 8-10 minutes of microwave heating is required to completely destroy enzymatic activity. 

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. 

A GST enzyme from pea Is very effective In catalyzing GSH conjugation of the herbicide fluorodlfen ( ). This enzyme has a pH optimum and other properties that are comparable to mammalian GST enzymes (85). This enzyme activity was observed In other plant species, but fluorodlfen resistant species appeared to have higher levels of this enzyme than susceptible species ( ). Additional studies with pea Indicated the presence of two soluble GST Isozymes, one that utilized fluorodlfen and one that utilized -cinnamic acid as substrates (W7). These Isozymes appeared to form aggregates during purification. In addition, a microsomal GST was detected In pea that utilized both -cinnamic acid and benzo(a)pyrene as substrates (WT.). Soybean cell suspension cultures metabolized -clnnamlc acid In a 6% yield to a product that corresponded to the GSH conjugate of t-clnnamlc acid by paper chromatography (107). 

Figure 2. Soil enzyme activity in soils treated with alachlor at a rate 100 ppm,amended with corn, soybean, or soybean+N, and inoculated with fungal isolate CCF-1.

Relatively few detailed studies have been performed on the GDH s of plants. An enzyme active with NAD but not NADP has been purified 1250-fold from pea roots (4S)- When assayed by reductive amination, however, the rate of reaction is 1.8 times faster with NADPH than NADH. An NAD-linked enzyme has been isolated from soybean cotyledons (47), and a similar enzyme from com leaves (4 ) has been shown not to be affected by purine nucleotides (17). 

Rosenthal, A. D.L. Pyle K. Niranjan S. Gilmour L. Trinca. Combined effect of operational variables and enzyme activity on aqueous enzymatic extraction of oil and protein from soybean, Enz. Microb. Technol. 2001,28, 499-509. 

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