Soluble protein isolate properties

Kinesin a soluble protein isolated from the axoplasm of squid giant axons apparent M, 600,000. In the presence of the non-hydrolysable ATP analog, adenylyl imidodiphosphate, it binds tightly to microtubules, but it is released from them by ATP. K. apparently consists of subunits of M, 110,000, 70,000 and 65,000. Polypeptides from bovine brain with similar binding properties and M, 120,000 and 62,000 have also been isolated. In the presence of ATP, K. causes... 

In particular, we have concentrated on developing techniques for isolating protein to attain this objective we have studied the practical use of chemical modification. The application of chemical modification to food proteins has been explored for several purposes to block deteriorative interactions between reactive groups (e.g., e-NH2 and reducing sugars) to improve functional properties (solubility, flavor, and thermal stability) to enhance nutritive value and digestibility to facilitate the elucidation of interrelationship between structure and functional properties (6,7,8,9) and, as discussed herein, to facilitate the preparation of protein isolates. 

The intermediate electron transfer between the pool of quinones accepting electrons from the RC, and the water soluble proteins donating electrons to the RC (bacterial RC and the PSI-RC) is always promoted, at least in the systems studied so far in detail, by a multiprotein complex containing cytochromes and Fe-S proteins, the so called h/ci complex. The universal presence of this type of complex in many redox chains of respiration and photosynthesis has been recognized only very recently [109]. As far as photosynthesis is concerned, complexes of this kind have been characterized in facultative photosynthetic bacteria [110] in cyanobacteria [111], and in higher plant chloroplasts [112]. All these preparations share common characteristics and composition these properties are also very similar to those of analogous complexes isolated from mitochondria of mammals and fungi [109]. 

It is now evident that acylation with anhydrides (such as acetic and succinic anhydrides) and with lactones (such as -propiolactone) is being proposed (< ) for improving the solubility of soy protein isolates at acidic pH, particularly for the preparation of coffee whiteners. Moreover, this chemical modification has been evaluated for altering the food-use properties of several milk proteins (40), egg protein (41), wheat protein (42), fish protein (43), and single-cell protein (44). 

Food proteins, especially those of plant origin, often require modification to achieve desirable functional properties for use as food ingredients. For instance, soy protein has limited water solubility at acid pH, which restricts its use in acidic foods such as coffee whitener and acidic beverages. Improved solubility at acid pH for commercial soy protein isolate can generally be achieved by hydrolysis. However, the hydrolysis has to be carefully controlled, because excessive peptide bond hydrolysis may release bitter peptides, resulting in undesirable off-flavors. Scientists are constantly looking for better and safer methods to improve the functional properties of protein to meet the needs of the food industry. 

Partial proteolysis of soy protein isolate with neutral protease from Aspergillus oryzae altered certain functional properties ( ). Solubility was increased in the enzyme-treated soy isolate at both neutral pH and at the isoelectric point (pH... 

SWP is a bland, white creamy low viscous sodium-salt of a soluble wheat protein isolate. By its unique combination of functional properties like emulsifying capacity, gelling, binding, and water-retention, the product can be used in several food applications like meat-preparations, soups, sauces, dressings, imitation dairy, etc. It can also be combined with other functional proteins like caseinates, soy isolates, and may result in all types of synergies. 

The subcellular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and in separated components of a protoplast lysate. The enzymes which were involved in the syntheses of starch were detected in the chloroplasts, whereas some of the enzymes involved in the degradation of starch were mainly in the soluble protein fraction but were also found in the chloroplast. The digestion pattern of the amylase on amylopectin as substrate indicated that the enzyme was an a-amylase from its endo-lytic activity, but displayed properties unlike the typical a-amylase isolated from endosperm tissue. A time-sequence analysis of the starch digestion pattern in germinating... 

Soluble proteins having the properties of serine hydroxymethyltransferase have been isolated and partly purihed from etiolated seedlings of Zea mays (Hauschild, 1959), the roots of tobacco Nicotiana rustica (Prather and Sisler, 1966), wheat leaves (Cossins and Sinha, 1966), and cauliflower buds (Mazelis and Lui, 1967). The properties of the enzymes vary considerably with source. Whilst the tobacco root enzyme showed a pH optimum of 4.0, the other enzymes had optima near or above 7.0. There may have been two isoenzymes in the preparation from cauliflower buds, one with an optimum at pH 7.5 and the other at pH 9.5. All the enzymes showed a requirement for pyridoxal phosphate and tetrahydrofolate. However, the fresh enzyme from tobacco roots showed little response to pyridoxal phosphate until it had been... 

---