Based on limited published evidence, VMA12 is an accessory component of the vacuolar V-ATPase proton pump critical for intracellular iron homeostasis. The protein is required for endolysosomal acidification and lysosomal protein degradation 1. In aerobic conditions, VMA12 maintains iron levels necessary for PHD enzyme activity, enabling HIF1A hydroxylation and proteasomal degradation 1. VMA12 may also contribute to Golgi homeostasis and binds 20(S)-hydroxycholesterol. Mutations cause congenital disorder of glycosylation 2P.