The kinetic parameters of aspartate transcarbamylase activity were determined in dialyzed extracts coming from ten different human normal and tumoral cell lines (three fibroblasts, four melanomas, and three colorectal carcinomas). Specific activities do not correlate with the malignant character of the cells but rather with the fact that the cells divide actively or not. Growth curves show large variations in the cell sensitivity to N-(phosphonacetyl)-l-aspartate (PALA). However, no differences in substrate affinity or PALA sensitivity of the aspartate transcarbamylase activities present in the corresponding cell extracts could be detected. Thus, the different human cell susceptibilities to PALA do not result from an intrinsic property of aspartate transcarbamylase. Cell death under the influence of PALA does not correlate with the tumoral or normal character of the cells.

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This work was supported by the Centre National de la Recherche Scientifique, the Institut National de la Santé et de la Recherche Médicale, and the Ligue Nationale Française contre le Cancer.

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