Metabolism of δ-acetylornithine in two leguminous species

Abstract

Experiments in which radioactive amino acids were supplied to germinating mung bean ( Phaseolus aureus Roxb.) and sainfoin ( Onobrychis viciifolia Scop.) showed that [2- 14C]ornithine was converted into a number of amino acids, in particular acetylomithine (sainfoin) and proline (mung bean), whilst δ-acetyl- [2- 14C]ornithine was converted into α,δ-diacetylornithine in both species. Synthesis of δ-acetylornithine was demonstrated in cell-free extracts of both species; N α-acetylated amino acids, acetylcoenzyme A and acetyl phosphate, but not N ω-acetylated amino acids, were shown to be effective acetylating agents. Coenzyme A was not required for direct transacetylation from N α-acetylated amino acids. In cell-free extracts δ-acetyl- [2- 14C]ornithine failed to act as either an acetyl donor or acceptor and no hydrolysis was detected. The discrepancies between in vivo and in vitro experiments are discussed.