Analysis of Proteins Occurring in Hevea Latex. II. Properties and Identification of the Isolated Products

Abstract

Abstract In a previous paper the separation and analysis of proteins remaining in rubber serum, after coagulating the rubber with formic acid, were described. The present paper is concerned with the properties and identification of the products thus isolated. As for nonamino acids, it may be recalled that these are composed mainly of the unsaponifiable thick brownish red oil A4. Of the other byproducts remaining to be identified, which were designated as BII, BIII, BV and BVI, only small amounts were obtained. Of the amino acids, alanine, arginine, asparagic acid, glutamic acid, histidine, leucine, ornithine, hydroxyproline, proline, tyrosine and valine were isolated in weighable amounts. In addition to these, it was possible to identify dihydroxyphenylalanine. In this connection the results obtained by Midgley, Henne and Renoll are of interest. These investigators found, as the principal components of proteins occurring in crepe rubber, the following amino acids: arginine, asparagic acid, glycine, histidine, leucine, lysine and proline. They considered it highly probable that alanine, phenylalanine, hydroxyproline and serine were also present in these proteins. On the other hand, it was definitely established that cystine, glutamic acid and tyrosine were not present. Table I summarizes the results of Midgley and his coworkers in comparison with ours. From this table it is evident that certain proteins, viz., those containing, among other compounds, tyrosine, glutamic acid and valine, do not coagulate with the rubber, but remain in the serum. The absence of sulfur-containing amino acids can probably be attributed to certain shortcomings in the analytical method. At any rate, the presence of sulfur in proteins precipitated from latex was established when the test was repeated.