ENDO-N-ACETYL-BETA-D-GLUCOSAMINIDASE AND PEPTIDE-N4-(N-ACETYL-GLUCOSAMINYL) ASPARAGINE AMIDASE ACTIVITIES DURING GERMINATION OF RAPHANUS-SATIVUS

Endo-N-acetyl-beta-D-glucosaminidase (ENGase, EC 3.2.1.96) and peptide -N-4-(N-acetyl-beta-D-glucosaminyl) asparagine amidase (PNGase, EC 3.5 .1.52) activities were monitored during germination and postgerminativ e development in Raphanus sativus. The PNGase activity was found in dr y seeds and its level was constant during germination and postgerminat ion. The ENGase activity was first detected about 18 hr after the star t of imbibition (HAI) and displayed a maximum level at 36 HAI. After 3 6 HAI the production of both enzymes was constant until days 4-5. Both enzymes displayed substrate specificities corresponding to the potent ial glycoprotein substrates found in plants. They are in agreement (i) with the hypothesis that ENGase and PNGase are at the origin of the p roduction of 'unconjugated N-glycans' and (ii) with the possibility th at protein activity could be regulated by the removal of N-glycans.