l-Glutamine:d-fructose 6-phosphate amidotransferase in tumors and the liver of tumor-bearing animals

Glucosamine 6-Phosphate Synthesis in Normal and Neoplastic Rat Tissues

“…A similar study of L-glutamine: D-fructose 6-phosphate aminotransferase (EC 2.6.1.16), the enzyme forming glucosamine 6-phosphate from glutamine and fructose 6-phosphate, is the subject of this paper. Most assays of this enzyme in animals have been limited to rat liver [1,3,11,20], but it was found in all rat tumors examined [5] and another study of its distribution in rat tissues was published after the present work was completed [4]. The results are generally similar, but comparison indicates that there may be unsolved problems in the analysis of this enzyme in certain tissues.…”

“…(A second value for lung, 5.9 in tumor-bearing rats [4], was significantly higher and equal to the other normal values cited in table III.) The differ ences appear unrelated to a new inhihitor demonstrated by Kikuchi et al [4] in soluble extracts of tumor, but not liver, if prepared in the presence of glucose 6-phosphate as were all of their tissue extracts.…”

“…Kikuchi et al [4] recently reported activities of amidotransferase for other rat tissues that can be compared with ours, but expressed tissue activi ties in their study per mg soluble protein. Since they did not give the protein concentrations of their several extracts, average tissue protein values compiled for this purpose [7] were used to calculate the Table III (table III).…”

“…Usually the conditions are sufficiently different between laboratories so that equal rates need not be expected, even though each are 'maximal capacities' for the particular conditions used. Thus, internally con sistent assays for adult rat liver have been reported as 60.0 [20], 55.6 [5], 31.0 [6], 63.0 [3], 24.0 [11], 82.0 [1] and 33.6 [4], in compari son with our values of 10-14, all expressed as nmoles/min/g tissue at 37° C. Harder centrifugation of the liver extracts [4,20] would appear to be more significant for producing the higher activities reported than homogenization in glucose 6-phosphate or other variations used in the above assays. Significant removal of product by a deaminase in liver does not occur [1].…”

“…Some tumors have elevated rates of synthesis of glycoproteins [17]. Tumor growth is often accompanied by a rise in plasma glycoproteins [4,21] which, because of the presence of this enzyme, may come from the tumor as well as the liver of the tumor-bearing animal. Glucosamine is itself used by ascitic tumor cells to alter their cell surfaces so as to promote intercellular adhesion, with effects to be expected on mor phogenesis, cell division and spread of the tumor cells [19].…”