抄録
The presence and enzymatic characters of each step in protein biosynthetic cell-free system of guinea pig brain were investigated.
1. Considerably high amino acids depen-dent PP32-ATP exchange activity, comparable to that of liver cell sap, was observed in brain cortex cell sap, although P32-ATP exchange was not demonstrable. Among three subfrac-tions of cell sap, the pH 4.5 fraction was found to be most active.
2. Amino acids are divided into three groups depending upon their efficiency on PP-ATP exchange by brain cell sap. Valine, tryptophan, methionine, alanine, threonine and lysine belong to the very effective amino acid group: tyrosine, histidine, glycine, serine, and isoleucine belong to the effective amino acid group: leucine, phenylalanine, proline, hydroxyproline, aspartic acid, asparagine, glu-tamic acid, glutamine, arginine, and γ-amino-butyric acid belong to the little or non-effec-tive amino acid group.
3. Active C14-leucine, and C14-valine in-corporation into s-RNA occurred in a system consisting of the precipitate of brain cell sap at pH 4.5, ATP and Mg++. Transfer of C14-glutamic acid to s-RNA was observed to be less active.
4. Existence of the transfer reaction of G14-leucine from s-RNA into microsomal pro-tein was observed in the presence of cell sap. This transfer was completed by about 10 min. ATP, ATP generating system and GTP were required for the transfer. Among three cell sap fraction pH 5.0 fraction was most active, followed by pH 4.5 fraction. The simultaneous addition of an excess amount of C12-leucine did not inhibit the transfer, although the leucine attachment to s-RNA reached its maximum at about one minute of incubation. The fact suggests very rapid rate of attachment of amino acyl s-RNA to microsomal templete. This attachment is followed by the peptide bond formation of more slow reaction rate.
5. These results may indicate that a series of enzymatic reactions: amino acid activation, attachment to s-RNA and transfer into microsomal protein, is actively operated in brain tissue.
