Catalyzes the ATP-dependent activation of L-glycine and its transfer to the phosphopantetheine prosthetic group covalently attached to the vicinal carrier protein blr6284 of yet unknown function. May participate in nonribosomal peptide synthesis or related processes. L-alanine is a poor substrate whereas L-serine or D-amino acids are not substrates for ATP-dependent activation. Does not display tRNA aminoacylation activity. an L-alpha-amino acid + ATP + holo-[ACP] = AMP + an L-alpha-aminoacyl-[ACP] + diphosphate Binds 1 Zn(2+) ion per subunit. The catalytic efficiency of the glycine activation reaction is 300-fold higher than that of alanine activation. Homodimer. Lacks the N-terminal tRNA-binding domain compared to class-II aminoacyl-tRNA synthetases. Belongs to the class-II aminoacyl-tRNA synthetase family. Amino acid--[acyl-carrier-protein] ligase subfamily.