Content of low-molecular-weight thiols during the imbibition of Pea seeds.

The metabolism of low-molecular-weight thiols was investigated in seeds of Pisum sativum L. cv. Kleine Rheinländerin during imbibition in water for 14 h. The amount of oxidized glutathione (GSSG) decreased from 319 nmol (g dry weight)-1 in dry seeds to 38 nmol (g dry weight)-1 within the first 14 h of imbibition. The decrease may have been due to the reduction of GSSG to reduced glutathione (GSH), catalyzed by the enzyme glutathione reductase (GR; EC 1.6.4.2). The enzyme activity was high in dry seeds [25 nkat (g dry weight)-1 ] and decreased to 20 nkat (g dry weight)-1 within 14 h of imbibition. The activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) decreased from 100 nkat (g dry weight)-1 in dry seeds to 67 nkat (g dry weight)-1 after 14 h of imbibition. Within 14 h the amount of γ-glutamyl-cysteine (γ-GC) decreased from 135 to 38 nmol (g dry weight)-1 , whereas the cysteine content rose from 81 nmol (g dry weight)-1 in dry seeds to a maximum of 170 nmol (g dry weight)-1 after 12 h of imbibition, which may be due to the degradation of γ-GC into cysteine.