Phenylalanyl synthetase function in cultured fibroblasts from subjects with progeria

Since progeria cells contain a diversity of altered proteins, some aspects of phenylalanyl synthetase function were examined in semipurified extracts of cultured skin fibroblasts using mixed rabbit tRNA as acceptor. No significant differences were found in the Km and Vmax for phenylalanine or ATP in progeria cells compared with controls. Initial velocities of both progeria and control synthetases were lower at late passage owing to either reduced enzyme content or reduced catalytic efficiency. Reverse phase 5 chromatography of tRNAs acylated by progeria and control synthetases gave a single peak of labeled phenylalanine tRNA in all cases with no secondary peaks evident. Total activity of phenylalanyl synthetase in progeria cells was similar to that of control cells at early passage while late-passage control cells had lower specific activities of these synthetases per unit protein.