Arginase from Lathyrus sativus

Abstract

The seeds of Lathyrus sativus contain the unusual amino acid homoarginine. The possible breakdown of homoarginine to lysine and urea has been investigated with enzyme extracts prepared from the seedlings of L. sativus. The results indicate that there is no separate homoarginase enzyme but that the arginase present has about 5 per cent activity towards L-homoarginine as compared to that obtained with L-arginine. The enzyme does not show an absolute dependence on Mn²⁺ for activity and maximal activation of the enzyme has been realized with Fe³⁺. It is concluded that the breakdown of homoarginine through the urea cycle may only represent a minor pathway for the catabolism of this compound in this plant.