Rapid purification of threonyl-tRNA synthetase from Saccharomyces carlsbergensis by affinity elution from phosphocellulose.

Threonyl-tRNA synthetase [EC 6.1.1.3] of Saccharomyces carlsbergensis was highly purified by a simple enzyme-substrate affinity method. After calcium-gel treatment of the crude enzyme extract, ammonium sulfate precipitation, and removal of polynucleotides with DEAE-cellulose, the enzyme was nonspecifically adsorbed onto phosphocellulose (P-cellulose), and then eluted specifically with a linear concentration gradient of threonine tRNA from torula yeast (Candida (Torulopsis) utilis). The enzyme was purified 303-fold from the calcium-gel supernatant. This purification method is very simple and time-saving. The purified enzyme gave a single band on SDS-gel electrophoresis, indicating a molecular weight of 82,000, and exhibited a molecular weight of about 150,000 by gel filtration. This suggests that the enzyme consists of two identical subunits. Some kinetic properties of the pure enzyme are described.