Enables glycine transmembrane transporter activity. Involved in glycine import across plasma membrane. Located in dense core granule; endosome; and plasma membrane. Is active in hippocampal mossy fiber to CA3 synapse; parallel fiber to Purkinje cell synapse; and postsynaptic density. Is integral component of postsynaptic membrane; integral component of presynaptic membrane; and integral component of synaptic vesicle membrane. Orthologous to human SLC6A9 (solute carrier family 6 member 9). [provided by Alliance of Genome Resources, Apr 2022]