L-isoglutamyl-polyglutamic acid L-isoglutamyl triglutamic acid 387.127777099609375 387.350006103515625 516.17034912109375 516.46002197265625 A protein modification that effectively converts an L-glutamic acid residue to isoglutamyl glutamyl-glutamyl-glutamic acid, forming an isopeptide bond with a triglutamic acid. C 15 H 21 N 3 O 9 C 20 H 28 N 4 O 12 E From DeltaMass: Average Mass: 388. GluGluGlu MOD:00874 N alpha -(gamma-Glutamyl)-Glu3 PSI-MOD Unimod:452 natural triglutamyl