Reaction: n ATP + [β-tubulin]-L-glutamate + n L-glutamate = [β-tubulin]-(γ-(poly-α-L-glutamyl)-L-glutamyl)-L-glutamate + n ADP + n phosphate (overall reaction)
(1a) ATP + [β-tubulin]-L-glutamate + L-glutamate = [β-tubulin]-(γ-L-glutamyl)-L-glutamate + ADP + phosphate
(1b) ATP + [β-tubulin]-(γ-L-glutamyl)-L-glutamate + L-glutamate = [β-tubulin]-(α-L-glutamyl-γ-L-glutamyl)-L-glutamate + ADP + phosphate
(1c) n ATP + [β-tubulin]-(α-L-glutamyl-γ-L-glutamyl)-L-glutamate + n L-glutamate = [β-tubulin]-(γ-(poly-α-L-glutamyl)-L-glutamyl)-L-glutamate + n ADP + n phosphate
Other name(s): β-tubulin polyglutamylase; TTLL4 (ambiguous); TTLL7 (ambiguous)
Systematic name: [β-tubulin]-L-glutamate:L-glutamate ligase (ADP-forming)
Comments: The eukaryotic tubulin proteins, which polymerize into microtubules, are highly modified by the addition of side-chains. The polyglutamylation reaction catalysed by this group of enzymes consists of two biochemically distinct steps: initiation and elongation. Initiation comprises the formation of an isopeptide bond with the γ-carboxyl group of the glutamate acceptor site, whereas elongation consists of the addition of glutamate residues linked by regular peptide bonds to the γ-linked residue. This entry describes enzymes that act on β-tubulins and other proteins with glutamate-rich regions but not on α-tubulins.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Regnard, C., Audebert, S., Desbruyeres, Denoulet, P. and Edde, B. Tubulin polyglutamylase: partial purification and enzymatic properties. Biochemistry 37 (1998) 8395-8404. [PMID: 9622491]
2. Regnard, C., Desbruyeres, E., Denoulet, P. and Edde, B. Tubulin polyglutamylase: isozymic variants and regulation during the cell cycle in HeLa cells. J. Cell Sci. 112 (1999) 4281-4289. [PMID: 10564646]
3. Ikegami, K., Mukai, M., Tsuchida, J., Heier, R.L., Macgregor, G.R. and Setou, M. TTLL7 is a mammalian β-tubulin polyglutamylase required for growth of MAP2-positive neurites. J. Biol. Chem. 281 (2006) 30707-30716. [PMID: 16901895]
4. van Dijk, J., Miro, J., Strub, J.M., Lacroix, B., van Dorsselaer, A., Edde, B. and Janke, C. Polyglutamylation is a post-translational modification with a broad range of substrates. J. Biol. Chem. 283 (2008) 3915-3922. [PMID: 18045879]