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Fundamentals of Biochemistry
A proposed pathway for ascorbic acid (vitamin
C) biosynthesis in plants takes the form D-glucose- 6 -phosphate $\stackrel{1}{\longrightarrow}$ D-fructose- 6 -phosphate $\stackrel{2}{\longrightarrow}$ D-mannose-6-phosphate $\longrightarrow$ D-mannose-1-phosphate 4
GDP-D-mannose $\stackrel{5}{\longrightarrow}$ GDP-L-galactose $\stackrel{6}{\longrightarrow}$ L-galactose-1-phosphate $\frac{7}{9}$ L-galactose L-galactono-1,4-lactone ? L-ascorbic acid
Match each of the following enzymes to one of the pathway steps.
(a) galactose dehydrogenase
(b) GDP-mannose-3,5-epimerase
(c) phosphoglucose isomerase
(d) phosphomannose isomerase
(e) phosphomannose mutase