Alkali-globulin

Cereal proteins when classified by the Osborne sequential extraction method yield four different classes albumins, which are water soluble, globulins, which are soluble in salt solutions, prolamins, which are soluble in alcohol-water mixtures, and glutelins, which are soluble in dilute acid or alkali. Chen and Bushuk added a fifth fraction by dividing the glutelin into two fractions, one soluble in dilute (0.05 m) acetic acid and the other insoluble in this reagent.5... 

Proteins historically have been classified on the basis of their solubility in water (albumins) salt solution (globulins) alcohol (prolamines) and alkali (glutelins) (20). 

A significantly higher amoimt of protein is found in beans from South Africa compared to beans from Botswana. The amount of protein in beans from Namibia is between the contents from the two other countries (Holse et al., 2010). The variation in protein content might be due to different concentration of nitrogen in the soils. Bower et al. (1988) found that globulins are the most abimdant (53%) protein constituents in morama beans. The beans furthermore consist of albumins (23.3%), prolamins (15.5%), alkali soluble glutelins (7.7%), and acid-soluble glutelins (0.5%). 

In the above methods, the separated albumin (or whole serum if total protein is to be determined) is reacted with excess copper in approximately 1 N alkali. A macromethod is also available which utilizes the capacity of albumin to react with copper(II) in a mole ratio of 1 1 (K32). This is an amperometric titration of blood serum (1 ml) in 0.1 M ammoniacal am-moniiun nitrate pH 9.2 with CuS04 (4.8 X 10 M). Under these conditions human y-globulin did not react, so that the fair agreement by this method with results obtained by a biuret method after sulfite fractionation (K32) is probably the result of a balance of errors. In view of the interest in the small fraction of albumin-boimd copper in hepatolenticular degeneration, and the paucity of information on the unique binding reaction presumably with N-terminal aspartyl residues, further investigation would be valuable. 

Wu (W30) discovered that the phenol reagent could be used to determine serum protein by adding it directly to serum diluted with alkali and comparing the color produced with that obtained from a standard tyrosine solution similarly treated. He determined the ratio by weight of protein to tyrosine and found it to be higher for albumin than for globulin (W30). In spite of claims to the contrary (A9, G21, M25), this difference... 

Time effects have also been observed for bovine plasma albumin, horse serum albumin and rabbit y-globulin (Beaven and Holiday, 1950). The behavior of bovine plasma albumin was most striking the intensity of the absorption in 0.1 N alkali increased steadily over a period of ca. 3 hours at room temperature the light-scattering properties of the solution, as shown by its apparent absorption on the long-wave side of the absorption band proper, also increased. Of the few proteins which were examined, only lysozyme showed no time effect. With trypsin the change in absorption was small and complete in a few minutes at pH 13, but the solution then became visibly turbid. 

Having proved that fortuitous phenomena and methodical imperfections have been eliminated, we shall try to propose an interpretation of the observed facts. The question of the increment in albumin due to denaturation seems to us to have been satisfactorily answered. However, the question of globulins is different their polarographic wave heights are increased by addition of alkali hydroxide only when the filter paper has remained in the solution serving as eluent. Let us discuss all possibilities concerning the behavior of globulins of diseased subjects, as follows ... 

Possibility 1 In a diseased person, a major part of globulins is primarily dissolved already in the added normal saline (0.9% NaCl) solution, and consequently the usual increase in solubility, due to the addition of alkali hydroxide, cannot substantially contribute to their further dissolution, which would lead to an increment in the wave height, in contrast to the circumstances existing in healthy subjects. 

Possibility 2 One procedure does not injure the globulins of diseased subjects so much as those of healthy ones (which would be a certain analogy with the heightened resistance of albumin, in disease, against denaturation), and this process would become apparent secondarily by an increased solubility already in the added normal saline (0.9% NaCl) solution. Consequently, after the addition of alkali hydroxide the increase would not be so high. We think that this interpretation is the most probable one. 

Possibility S Globulin of both healthy and diseased subjects is soluble in the same ratio before and after the addition of alkali hydroxide, but in disease the less soluble part, sticking to the filter paper, exposes fewer active groups under the action of alkali hydroxide than is the case in good health. 

We bring proofs that pathological proteins have a different quality, whieh is discernible by polarography and is manifested by a smaller increase in the wave height after denaturation by alkali hydroxide in albumin, and by a diminished elution from the paper into the solution after addition of alkali hydroxide in globulins. In globulin fractions, the nature of proteins is typically changed above all at the very places where... 

Analogous results were repeatedly obtained, indicating that the mechanism of exposing polarographically active groups is evidently very similar even in processes so dissimilar as proteolysis and denaturation of albumin by alkali hydroxide. In globulins the mechanism of dissolution seems to be subject to an analogous influence. 

---