Peroxisomal Biogenesis Factor 19 (PEX19) is part of a group of constitutive housekeeping genes termed peroxins that are involved in peroxisome biogenesis. PEX19 encodes a predominantly cytoplasmic protein that binds the hydrophobic domains of class I peroxisomal membrane proteins (PMP); PEX19 stabilizes and targets PMPs towards peroxisome assembly. PEX19-PMP binds the peroxisome transmembrane protein PEX3 in order to facilitate importing of class I PMPs into the peroxisome membrane. PEX19 is additionally thought to downregulate tumorsuppressor function; the peroxin interacts with p19ARF in the cytoplasm restricting its access to the nucleolus, where it normally prevents transcriptional silencing of p53 and Mdm2 mediated degradation of p53.
Peroxin dysfunction clinically results in various subtypes of Zellweger syndrome, the most severe phenotypic class of peroxisome biogenesis disorders. PEX19 dysfunction is specifically associated with autosomal recessive peroxisome biogenesis disorder 12A (PBD12A).