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GNPTABA gene on chromosome 12q23.2 that encodes two of three subunit types of the membrane-bound enzyme N-acetylglucosamine-1-phosphotransferase, a heterohexameric complex composed of 2 alpha, 2 beta and 2 gamma subunits. The encoded protein is proteolytically cleaved to yield mature alpha and beta polypeptides (the gamma subunits are the product of GNPTG). In the Golgi apparatus, the complex catalyses the first step in the synthesis of mannose 6-phosphate recognition markers on oligosaccharides of lysosomal enzyme, which are essential for lysosomal enzyme-targeted trafficking.
GNPTAB mutations are linked to mucolipidosis II (I cell disease) and mucolipidosis IIIA (pseudoHurler polydystrophy).