Prüfung auf das Vorkommen von d-Glutaminsäure in Eiweiß von malignen Tumoren und von normalen Organen

Abstract

Most proteins in the body contain about 10% glutamic acid, but some plant proteins contain much greater amts. d,l-Glutamic acid HC1 is about twice as soluble in H2O as 1-glutamic acid HC1. In a protein hydrolysate it is difficult to separate glutamic acid from phenylalanine, cystine, arginine, leucine, and isoleu-cine. If the glutamic acid isolated is recrystallized 3 times, and if the products of each recrystallization are identical, the glutamic acid is considered to be pure. The tumors or tissues are hydrolyzed by heating 6-8 hrs. with 3 vols. HC1. The hydrolysate is evaporated to dryness under 10-15 mm. pressure, the residue dissolved in H2O and the soln. decolorized with charcoal. The soln. is concd., saturated with HC1 gas at room temp., inoculated with crystals of 1-glutamic acid HC1, and placed in the ice box about 8-10 days. The crystals formed are filtered off, dissolved in H2O, and the soln. concd, under diminished pressure. The syrup obtained is mixed with absolute alc, saturated with HCl gas and filtered. The nitrate is evaporated to dryness in vacuo, the residue refluxed for 2 hrs. with 20% aqueous HCI, and crystals of 1-glutamic acid HCI obtained. The mother liquor is concd, and crystals of d,l-glutamic acid HCI recovered. The acids are identified by their optical rotation in 20% HCI. Tissues studied include normal liver, spleen, stomach wall, skeletal and heart muscle, and carcinoma of the stomach, intestinal canal, uterus, liver metastases etc. Only 1-glutamic acid is found in normal tissues, while a small amt. of d-giutamic acid, much less than that reported by Kogl and Erxleben, is found in some tumors. Amino acids of the d-series do not seem to be involved necessarily in the origin of tumor or carcinoma cells. The presence of d-amino acids in tumors may be due to failure of the enzyme system.