[Isolation and purification of aspartyl- and valyl-tRNA-synthetases from muscles of normal and long-fasting rabbits. Structural characteristics and various kinetic parameters].

Highly purified aspartyl- and valyl-tRNA synthetases were obtained by 6-stage purification from normal and long-fasting rabbit's muscles. The molecular masses of the enzymes are (120 +/- 10) X 10(3). These proteins consist of two subunits (alpha 2-type) with (60 +/- 10) X X 10(3) molecular mass as determined by electrophoresis in SDS polyacrylamide gel. The values of Km for ATP are similar for all the studied enzymes (4.25 divided by 6.48) M X 10(-3) but Km for amino acids differ: (1.22 divided by 3.3) M X 10(-4) for normal and (13.8 divided by 18.9) X M-4 for enzymes from long-fasting rabbits. The molecular activity of the latter increases 2.5-3 fold.