Enhancement of the activity of asparaginyl-tRNA synthetase by an activator from rabbit liver.

Asparaginyl-tRNA synthetase has been partially purified from acetone powders of rabbit liver. (NH-4)-2SO-4 fractionation was followed by chromatography of the enzyme on DEAE-cellulose. An activator separated from the enzyme. Further chromatography on Sephadex G-100 and G-200 showed that the latter consisted of two components. The smaller of these (mol wt is approximately equal to 35 000) possessed enzyme transfer activity but the larger one (mol wt 80 000-90 000) required the addition of activator before any enzyme transfer activity was demonstrable. The activator itself was devoid of transfer activity. After chromatography of crude extracts of asparaginyl-tRNA synthetase on Sepharose 4B the activity in the enzyme peak, which was of considerably larger molecular weight than any of the fractions found after purification could be enhanced by addition of the activator. None of the fractions of the enzyme or of activator catalysed any extensive asparagine-dependent ATP-PP-i exchange, either in the presence or the absence of added tRNA.