Epimerization of D-glucose to L-galactose during the biosynthesis of a sulfated L-galactan in the ascidian tunic

Journal Article · Tue Apr 09 04:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00228a016· OSTI ID:5558000

Mourao, P A.S. ^[1]

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1. Universidade Federal do Rio de Janeiro (Brazil)

The sulfated polysaccharides occurring in the tunic of ascidians are unique among known sulfated polysaccharides in that their major constituent sugar is galactose, which occurs exclusively in the L-enantiomeric form. In vitro incorporation experiments using tunic slices incubated with {sup 14}C-labeled sugars revealed that cells from this tissue epimerize D-isomers of hexose into L-galactose during the biosynthesis of their constituent polysaccharides. Compared with other hexoses, the precursor D-({sup 14}C)glucose has the highest rate of incorporation and produces the highest proportion of L-galactose units. This metabolic pathway is distinct from the epimerization of D-mannose to L-galactose through its guanosine 5{prime}-diphosphate nucleotide, described previously in an alga and in a snail. Therefore, the epimerization of D-glucose to L-galactose in the ascidian tunic occurs through a novel metabolic route, which involves inversion of the configuration of carbon atoms 2, 3, and 5 of the hexosyl moieties.

• OSTI ID: 5558000
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:14; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
BIOLOGICAL PATHWAYS
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CHEMICAL REACTIONS
ELECTROPHORESIS
ENANTIOMORPHS
GALACTOSE
GLUCOSE
HEXOSES
HYDROGEN COMPOUNDS
LABELLED COMPOUNDS
MONOSACCHARIDES
ORGANIC COMPOUNDS
OXIDATION
POLYSACCHARIDES
SACCHARIDES
TRITIUM COMPOUNDS