ATP-dependent microtubule severing protein that specifically recognizes and cuts microtubules that are polyglutamylated.Preferentially recognizes and acts on microtubules decorated with short polyglutamate tails: severing activity increases as the number of glutamates per tubulin rises from one to eight, but decreases beyond this glutamylation threshold . Severing activity is not dependent on tubulin acetylation or detyrosination.