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. Microtubule severing promotes reorganization of cellular microtubule arrays and the release of microtubules from the centrosome following nucleation. Required for membrane traffic from the endoplasmic reticulum (ER) to the Golgi and for completion of the abscission stage of cytokinesis. Also plays a role in axon growth and the formation of axonal branches. n ATP + n H2O + a microtubule = n ADP + n phosphate + (n+1) alpha/beta tubulin heterodimers. Homohexamer. The homohexamer is stabilized by ATP-binding. The homohexamer may adopt a ring conformation through which microtubules pass prior to being severed. Interacts with microtubules. Forms an intramembrane hairpin-like structure in the membrane. Maternally expressed. Expressed at low levels throughout the embryo up to 24 hours post-fertilization (hpf). Branchiomotor neurons exhibit reduced axonal outgrowth and aberrant positioning of neuronal cell bodies. Outgrowth of motor axons from the spinal cord is impaired, the number and length of spinal motor neurons is reduced, and elevated levels of apoptosis are observed in the CNS. Thickened bundles of axonal microtubules are observed in the spinal cord. Longitudinal fascicles in the hindbrain are disordered. Most embryos are immotile and fail to hatch, while those that do exhibit reduced motility and swimming defects. Morpholino knockdown results in abnormal morphological features, including hydrocephalia, perturbed yolk sac extension and an arched-back phenotype, disorganized microtubule networks in the spinal cord and thinner microtubules in the spinal motor neuron axons, and in increased oxidative stress (PubMed:26744324). These phenotypes are rescued following exposure to the drugs methylene blue, guanabenz, salubrinal or phenazine (PubMed:26744324). Belongs to the AAA ATPase family. Spastin subfamily.