TY - JOUR
T1 - Functions of the α, β, and γsubunits of UDP-GlcNAc:Lysosomal enzyme N-acetylglucosamine-1-phosphotransferase
AU - Qian, Yi
AU - Lee, Intaek
AU - Lee, Wang Sik
AU - Qian, Meiqian
AU - Kudo, Mariko
AU - Canfield, William M.
AU - Lobel, Peter
AU - Kornfeld, Stuart
PY - 2010/1/29
Y1 - 2010/1/29
N2 - UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase is an α2β2γ2 hexamer that mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on lysosomal acid hydrolases. Using a multifaceted approach, including analysis of acid hydrolase phosphorylation in mice and fibroblasts lacking the γ subunit along with kinetic studies of recombinant α2β 2γ2 and α2β2 forms of the transferase, we have explored the function of the α/βand γ subunits. The findings demonstrate that the α/β subunits recognize the protein determinant of acid hydrolases in addition to mediating the catalytic function of the transferase. In mouse brain, the α/βsubunits phosphorylate about one-third of the acid hydrolases at close to wild-type levels but require the γ subunit for optimal phosphorylation of the rest of the acid hydrolases. In addition to enhancing the activity of the α/β subunits toward a subset of the acid hydrolases, the γ subunit facilitates the addition of the second GlcNAc-P to high mannose oligosaccharides of these substrates. We postulate that the mannose 6-phosphate receptor homology domain of the γ subunit binds and presents the high mannose glycans of the acceptor to the α/β catalytic site in a favorable manner.
AB - UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase is an α2β2γ2 hexamer that mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on lysosomal acid hydrolases. Using a multifaceted approach, including analysis of acid hydrolase phosphorylation in mice and fibroblasts lacking the γ subunit along with kinetic studies of recombinant α2β 2γ2 and α2β2 forms of the transferase, we have explored the function of the α/βand γ subunits. The findings demonstrate that the α/β subunits recognize the protein determinant of acid hydrolases in addition to mediating the catalytic function of the transferase. In mouse brain, the α/βsubunits phosphorylate about one-third of the acid hydrolases at close to wild-type levels but require the γ subunit for optimal phosphorylation of the rest of the acid hydrolases. In addition to enhancing the activity of the α/β subunits toward a subset of the acid hydrolases, the γ subunit facilitates the addition of the second GlcNAc-P to high mannose oligosaccharides of these substrates. We postulate that the mannose 6-phosphate receptor homology domain of the γ subunit binds and presents the high mannose glycans of the acceptor to the α/β catalytic site in a favorable manner.
UR - http://www.scopus.com/inward/record.url?scp=77449112978&partnerID=8YFLogxK
U2 - 10.1074/jbc.M109.068650
DO - 10.1074/jbc.M109.068650
M3 - Article
C2 - 19955174
AN - SCOPUS:77449112978
SN - 0021-9258
VL - 285
SP - 3360
EP - 3370
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 5
ER -