Seems to facilitate zinc transport from the cytoplasm into the Golgi apparatus. Partly regulates cellular zinc homeostasis. Required with ZNT5 for the activation of zinc-requiring enzymes, alkaline phosphatases (ALPs). Transports zinc into the lumens of the Golgi apparatus and the vesicular compartments where ALPs locate, thus, converting apoALPs to holoALPs. Required with ZNT5 and ZNT6 for the activation of TNAP (By similarity). Homooligomer. Highly expressed in liver, spleen, duodenum and part of the jejunum of small intestine (at protein level). Moderately expressed in kidney, lung, and brain. Barely detectable in heart. Null mutants are viable, fertile, and display no obvious morphological abnormalities. However, reduced food intake (anorexia) and poor growth were observed. Belongs to the cation diffusion facilitator (CDF) transporter (TC 2.A.4) family. SLC30A subfamily.