Partial purification and characterization of 4-hydroxycinnamic acid: CoA Ligase (EC. 6.2.1.12) from resistant and susceptible tomato cultivars inoculated with Meloidogyne incognita

The specific activity of 4-hydroxycinnamic acid: CoA ligase was assayed using p-coumaric acid as a substrate at an early stage of infection with the root-knot nematode, Meloidogyne incognita in both susceptible (Pusa Ruby) and resistant (Nemamukt and Hisar Lalit) cultivars of tomato. The activity was higher in resistant cultivars Nemamukt (18.0 to 150.8%) and Hisar Lalit (34.2 to 162.7%) at different time intervals compared to susceptible cv. Pusa Ruby (15.0 to 40.0%). The number of isozymes increased from 3 to 6 in resistant cultivars but remained unchanged in susceptible one. The relative specific activity of the enzyme was 15 and 20-fold during the purification process in resistant and susceptible cultivars, respectively. The enzyme activity was maximum at 25–30°C with pH ranging from 7.5 to 8.5 and p-coumaric acid was judged to be the best substrate. The involvement of CoA ligase in host-parasite interaction is indicated.