Leucine specific transfer ribonucleic acids and synthetases in the cotyledons of mature and germinating pea seeds

Abstract

Changes in isoaccepting species of tRNA Leu were determined in germinating pea seedlings and in developing pods. Leucine specific transfer ribonucleic acids of pea cotyledons can be fractionated into four isoaccepting species by reversed-phase chromatography (RPC-5) on a Plaskon column. In contrast, only two species of tRNA Leu were observed in developing seed pods. Leucyl- tRNA synthetase purified by ammonium sulfate precipitation and DEAE cellulose column chromatography retained the full range of specificity towards all four tRNA Leu species of pea cotyledons. This partially purified pea cotyledon enzyme could be further separated on a hydroxylapatite (HA) column into two peaks of leucyl- tRNA synthetase activity. Enzyme 1 is dominant in seed pods while 2 is predominant in cotyledons. Enzymes 1 and 2 from cotyledons were examined for the amino acid acceptor activity of twelve different amino acids. Both these fractions showed less than 3% acceptor activity for eleven other amino acids as compared to leucine- tRNA synthetase activity. Preliminary characterization of enzyme 2 from cotyledon, by isoelectric focusing and polyacrylamide gel electrophoresis indicates at least three subspecies.