Decarboxylation of homoarginine and lysine by an enzyme from Lathyrus sativus seedlings

Abstract

Homoarginine decarboxylase has been purified ca 110-fold from Lathyrus sativus seedlings and resolved from arginine decarboxylase by DEAE-Sephadex column chromatography. The enzyme was less active than arginine decarboxylase and was highly labile. This preparation decarboxylated l-lysine in addition to L-homoarginine. The purified enzyme preparation had an absolute requirement for exogenous Mn²⁺ or Fe²⁺ for both the enzyme activities. The pH and temperature optima for decarboxylation of both homoarginine and lysine were the same viz. 8.4 and 41° respectively. The K_m value l-homoarginine was 3.33 mM and for L-lysine was 0.88 mM. Arginine and homoarginine decarboxylases appear to be different and separable entities having different physico-chemical characteristics, despite the fact that their respective guanido amino acid substrates undergo similar metabolic conversion to guanido- and diamines in this plant system.