Monoglycylase which modifies both tubulin and non- tubulin proteins, generating side chains of glycine on the gamma- carboxyl groups of specific glutamate residues of target proteins. Monoglycylates tubulin, with a preference for alpha-tubulin toward beta-tubulin. Has the ability to modify non-tubulin proteins such as ANP32A, ANP32B, SET and NCL. Involved in the side-chain initiation step of the glycylation reaction by adding a single glycine chain to generate monoglycine side chains. Not involved in elongation step of the polyglycylation reaction.