Glutamic Acid in Malignant Tumors

The ultimate solution of the problem of cancer will probably involve the recognition of specific chemical differences between the modes of development of normal and of neoplastic cellular tissues. The growth of a tissue comprises the synthesis of protein from the natural amino acids. It has in the past few years become amply clear that all amino acids occurring in proteins have the same “natural” steric configuration, and that all proteins on hydrolysis yield only the l-amino acids (with allowance for any racemization’ that may have been brought about by the hydrolytic agent). In a recent article on the etiology of malignant tumors Kijgl and Erxleben (1) report the presence of “unnatural” amino acids, notably glutamic acid, in the products of hydrolysis of malignant tumors. Glutamic acid mixtures containing as high as 44.5 per cent of the d(-) (i.e. 89 per cent of the dl) form were isolated from six malignant tumors, in contrast to which only the Z(+) form was obtained from six normal specimens of tissue and one uterine myoma. This article communicates our complete failure to confirm these findings of Kiigl and Erxleben. In a series of six malignant tumors we have found only I(+)-glutamic acid. K6gl and Erxleben isolated glutamic acid directly as the hydrochloride from either the whole hydrolysate or from the fraction remaining after butyl alcohol extraction; whereas our isolations of glutamic acid hydrochloride were from the dicarboxylic acid fraction prepared by precipitation of the barium salts with alcohol. It is not likely that our failure to find dLglutamic acid is due to this difference in procedure, for Foster2 has isolated