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2.7.7.69

GDP-L-galactose/GDP-D-glucose: hexose 1-phosphate guanylyltransferase

(1) GDP-β-L-galactose + α-D-mannose 1-phosphate = β-L-galactose 1-phosphate + GDP-α-D-mannose;;(2) GDP-α-D-glucose + α-D-mannose 1-phosphate = α-D-glucose 1-phosphate + GDP-α-D-mannose

VTC2, VTC5, GDP-L-galactose phosphorylase

GDP-β-L-galactose/GDP-α-D-glucose:hexose 1-phosphate guanylyltransferase

This plant enzyme catalyses the conversion of GDP-β-L-galactose and GDP-α-D-glucose to β-L-galactose 1-phosphate and α-D-glucose 1-phosphate, respectively. The enzyme can use inorganic phosphate as the co-substrate, but several hexose 1-phosphates, including α-D-mannose 1-phosphate, α-D-glucose 1-phosphate, and α-D-galactose 1-phosphate, are better guanylyl acceptors. The enzyme's activity on GDP-β-L-galactose is crucial for the biosynthesis of L-ascorbate.

created 2010, modified 2020