Murine UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase lacking the gamma-subunit retains substantial activity toward acid hydrolases.
UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on acid hydrolases. The transferase exists as an alpha(2)beta(2)gamma(2) hexameric complex with the alpha- and beta-subunits derived from a single precursor molecule. The catalytic function of the transferase is attributed to the alpha- and beta-subunits, whereas the gamma-subunit is believed to be involved in the recognition of a conformation-dependent protein determinant common to acid hydrolases. Using knock-out mice with mutations in either the alpha/beta gene or the gamma gene, we show that disruption of the alpha/beta gene completely abolishes phosphorylation of high mannose oligosaccharides on acid hydrolases whereas knock-out of the gamma gene results in only a partial loss of phosphorylation. These findings demonstrate that the alpha/beta-subunits, in addition to their catalytic function, have some ability to recognize acid hydrolases as specific substrates. This process is enhanced by the gamma-subunit.
Lee
Wang-Sik
WS
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110 and.
Payne
Bobby Joe
BJ
Lexicon Pharmaceuticals, Inc., The Woodlands, Texas 77381.
Gelfman
Claire M
CM
Lexicon Pharmaceuticals, Inc., The Woodlands, Texas 77381.
Vogel
Peter
P
Lexicon Pharmaceuticals, Inc., The Woodlands, Texas 77381.
Kornfeld
Stuart
S
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110 and. Electronic address: skornfel@wustl.edu.
D000818:Animals; D001921:Brain / Q000201:enzymology; D002384:Catalysis; D002402:Cathepsin D / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism*; D008247:Lysosomes / Q000201:enzymology; D008358:Mannose / Q000378:metabolism; D051379:Mice; D009844:Oligosaccharides / Q000378:metabolism; D010766:Phosphorylation; D021122:Protein Subunits; D013379:Substrate Specificity; D017855:Transferases (Other Substituted Phosphate Groups) / Q000737:chemistry* / Q000378:metabolism
D009844:Oligosaccharides; D021122:Protein Subunits; D017855:Transferases (Other Substituted Phosphate Groups); C030012:UDP-N-acetylglucosamine-lysosomal-enzyme-N-acetylglucosaminephosphotransferase; D006867:Hydrolases; D002402:Cathepsin D; D008358:Mannose