Catalytic subunit of a complex which severs microtubules in an ATP-dependent manner. Microtubule severing may promote rapid reorganization of cellular microtubule arrays and the release of microtubules from the centrosome following nucleation. Microtubule release from the mitotic spindle poles may allow depolymerization of the microtubule end proximal to the spindle pole, leading to poleward microtubule flux and poleward motion of chromosome. The function in regulating microtubule dynamics at spindle poles seems to depend on the association of the katanin KATNA1:KATNB1 complex with ASPM which recruits it to microtubules. Reversely KATNA1:KATNB1 can enhance ASPM blocking activity on microtubule minus-end growth. Microtubule release within the cell body of neurons may be required for their transport into neuronal processes by microtubule-dependent motor proteins. This transport is required for axonal growth. n ATP + n H2O + a microtubule = n ADP + n phosphate + (n+1) alpha/beta tubulin heterodimers. ATPase activity is stimulated by microtubules, which promote homooligomerization. ATP-dependent microtubule severing is stimulated by interaction with KATNB1. Can homooligomerize into hexameric rings, which may be promoted by interaction with microtubules. Interacts with KATNB1, which may serve as a targeting subunit (By similarity). Interacts with ASPM; the katanin complex formation KATNA1:KATNB1 is required for the association of ASPM (PubMed:28436967). Interacts with dynein and NDEL1. Associates with the E3 ligase complex containing DYRK2, EDD/UBR5, DDB1 and DCAF1 proteins (EDVP complex). Interacts with KLHL42 (via the kelch domains). Interacts with CUL3; the interaction is enhanced by KLHL42 (By similarity). Interacts with KATNB1 and KATNBL1 (By similarity). Interacts with CAMSAP2 and CAMSAP3; leading to regulate the length of CAMSAP-decorated microtubule stretches (By similarity). Predominantly cytoplasmic. Localized diffusely in the cytoplasm during the interphase. During metaphase is localized throughout the cell and more widely dispersed than the microtubules. In anaphase and telophase is localized at the midbody region. Also localized to the interphase centrosome and the mitotic spindle poles. Enhanced recruitment to the mitotic spindle poles requires microtubules and interaction with KATNB1 (By similarity). Localizes within the cytoplasm, partially overlapping with microtubules, in interphase and to the mitotic spindle and spindle poles during mitosis (By similarity). Elevated during early neuronal development. Expressed in dorsal root ganglia and peripheral and central processes of sensory neurons at 13 dpc. Also expressed in neurons and axons of the embryonic tectum at 13 dpc, and in the cerebral cortex at 16 dpc. Highly expressed in layers containing hippocampal neurons at P1, with expression becoming undetectable by P8. The N-terminus is sufficient for interaction with microtubules, although high affinity binding to microtubules also requires an intact C-terminal domain and ATP, which promotes oligomerization. Phosphorylation by DYRK2 triggers ubiquitination and subsequent degradation. Ubiquitinated by the BCR(KLHL42) E3 ubiquitin ligase complex, leading to its proteasomal degradation. Ubiquitinated by the EDVP E3 ligase complex and subsequently targeted for proteasomal degradation. Belongs to the AAA ATPase family. Katanin p60 subunit A1 subfamily.